Fuel Injection Rewiring...
Discussion
Oh, you know, just another one of those little jobs on a Wedge... 
Ever since I got the 390 I've been aware that the fuel injection loom is suffering from the ravages of 16 years cooped up in a hot engine bay (brittle wires, cracked insulation, corroding copper, that kind of thing).
Several of the injector connectors have been less than willing to stay firmly attached, in some cases owing to the spring latches having disappeared. Closer inspection also showed that some of the contact 'fingers' were damaged as well.
I've always been puzzled about the apparent uneven running of my car at idle, and wondered if the wiring may be contributing a bit. Or a lot. My ECU has been tried on another Wedge, and it was as smooth as silk. I've had test meters and 'scopes and stuff on the electronics, but haven't proved anything to be at fault. So maybe it's just down to the cam. To be on the safe side, even though I had the cam out 4000 miles ago, I did a top-end strip just to check it, and things like the followers. Can't see anything wrong there.
OK, so let's look at ripping all the FI wiring off and replacing it. At first I considered going to a breakers and filling my pockets with spare connectors and so on, but the resultant soldering job would have been a pain.
Then I found the correct 2-pin connectors hiding in the Vehicle Wiring Products catalogue. So that was it - a proper job was called for.
It turns out that VWP also supply the 7-pin connector for the airflow meter. Until recently they even supplied the 3-pin for the throttle pot, but the connector range is now obsolete. Typical. However, they still have thousands of the actual terminals in stock, so as long as the housings are serviceable, no problem. That leaves the power resistor pack. Careful measurement and comparison with their photos turned up the correct terminals, but the housings are a bit obscure, so need to be reclaimed.
The ECU, AFM, all the injectors, both temp sensors and the thermotime switch all use the same type of terminal. The ECU connector housings are reusable - just as well 'cos I don't know where to get a new one!
To do the job as 'original' as possible I ordered wire in 30 different colours (well, that's what's on the car!!).
I stripped the old wiring out, leaving a few in place on the ECU as they weren't worth changing for such short runs - anyway most of the 'trauma' is in the engine bay.
Starting with the injectors and sensors, I then wired the AFM and resistor pack, producing the main body of the loom ready to pass through to the ECU. I routed a little differently to the old loom to avoid crossing the rocker covers etc. All joints are soldered, incidentally.
TVR seem to have simply lifted the loom straight from whichever V8 Rover was in production at the time, so it's at least a metre longer than it needs to be - I'm cutting the new one as short as possible to keep it tidy. I just have to finish off the ECU end and then I can fire up for a test before I wrap the loom. I was planning on building-in a test box of some sort to make fault diagnosis quicker: haven't finalised that bit yet!
Costs so far: about GBP65 for all materials, plus a long evening's work. Now I'll probably find that I could have bought an off-the-shelf loom for twenty quid...
Ian
Ever since I got the 390 I've been aware that the fuel injection loom is suffering from the ravages of 16 years cooped up in a hot engine bay (brittle wires, cracked insulation, corroding copper, that kind of thing).
Several of the injector connectors have been less than willing to stay firmly attached, in some cases owing to the spring latches having disappeared. Closer inspection also showed that some of the contact 'fingers' were damaged as well.
I've always been puzzled about the apparent uneven running of my car at idle, and wondered if the wiring may be contributing a bit. Or a lot. My ECU has been tried on another Wedge, and it was as smooth as silk. I've had test meters and 'scopes and stuff on the electronics, but haven't proved anything to be at fault. So maybe it's just down to the cam. To be on the safe side, even though I had the cam out 4000 miles ago, I did a top-end strip just to check it, and things like the followers. Can't see anything wrong there.
OK, so let's look at ripping all the FI wiring off and replacing it. At first I considered going to a breakers and filling my pockets with spare connectors and so on, but the resultant soldering job would have been a pain.
Then I found the correct 2-pin connectors hiding in the Vehicle Wiring Products catalogue. So that was it - a proper job was called for.
It turns out that VWP also supply the 7-pin connector for the airflow meter. Until recently they even supplied the 3-pin for the throttle pot, but the connector range is now obsolete. Typical. However, they still have thousands of the actual terminals in stock, so as long as the housings are serviceable, no problem. That leaves the power resistor pack. Careful measurement and comparison with their photos turned up the correct terminals, but the housings are a bit obscure, so need to be reclaimed.
The ECU, AFM, all the injectors, both temp sensors and the thermotime switch all use the same type of terminal. The ECU connector housings are reusable - just as well 'cos I don't know where to get a new one!
To do the job as 'original' as possible I ordered wire in 30 different colours (well, that's what's on the car!!).
I stripped the old wiring out, leaving a few in place on the ECU as they weren't worth changing for such short runs - anyway most of the 'trauma' is in the engine bay.
Starting with the injectors and sensors, I then wired the AFM and resistor pack, producing the main body of the loom ready to pass through to the ECU. I routed a little differently to the old loom to avoid crossing the rocker covers etc. All joints are soldered, incidentally.
TVR seem to have simply lifted the loom straight from whichever V8 Rover was in production at the time, so it's at least a metre longer than it needs to be - I'm cutting the new one as short as possible to keep it tidy. I just have to finish off the ECU end and then I can fire up for a test before I wrap the loom. I was planning on building-in a test box of some sort to make fault diagnosis quicker: haven't finalised that bit yet!
Costs so far: about GBP65 for all materials, plus a long evening's work. Now I'll probably find that I could have bought an off-the-shelf loom for twenty quid...
Ian
Hmmm. Well, I seem to have opened a box of crap with this job.
To carry on from the above, I finished off the injection loom (back to the ECU), leaving it tied with releasable ties just in case.
Anyway, put the plugs back in, topped up the coolant... and it wouldn't start. Oh. eventually I realised that I'd forgotten to reconnect the trigger from the distributor.... doh!
So, with that fixed, I turned the key.
What a sack of sh!t. The worst idle I've ever seen on a V8. Remember that one of the symtoms I was hoping to cure was rough idle and poor off-idle response. So now it's even worse. Bizarre.
I went through the entire injection system, checked every colour, every connection, verified that things were where they should be. All OK.
Then I did it again
Now I should add that I've just renewed the inlet manifold gasket and rocker cover gaskets (the former with a composite, the latter with the latest rubber items). There was nothing wrong with te camshaft or followers, and apart from cleaning off old sealant I did nothing else to the engine while it was in bits.
So far I've checked:
Correct connection of fuel pipes to regulator (feed to rail, return from FPR).
Fuel rail pressure - 2.8 bar at idle, reducing with manifold vacuum. Can be adjusted as high as 3.5 bar, at which setting the idle sems to improve... abit.
Response of water temp sensor: fine - the sensor is about a year old. I changed it on the offchance back then, but it made no difference to anything.
Response and correct setting (300mV) of throttle pot. Output rises to just over 4V at full throttle. No evident noise from wiper. With the ignition on, if you 'flick' the throttle open at any part of its range, you can hear the injectors all fire as the ECU thinks you've just nailed it.
Resistances and voltages at airflow meter in accordance with that specified (data from Joolz). Pot response OK, no noise. Temp sensor about 1.2K with AFM hot. Fuel pump switch OK.
All injectors can be triggered by grounding their feed at the ECU connector. Each injector takes about 1.33 - 1.36A.
Water temp sensor, throttle pot, AFM pot and AFM temp sensor can all be measured at the correct pins of the ECU connector.
With the cover off the ECU and the engine running, the ECU 5V rail is correct. You can observe ignition trigger pulses on the PCB, and the output pulses firing the injectors.
You can physically hear and feel the injectors firing.
Ignition timing is about 8 deg BTDC as it always has been while I've had the car.
There is no coolant leakage or any evident air leaks around the inlet manifold, trumpet base or plenum chamber.
There is no cold start injector.
The exhaust gas smells well over-rich. The idle is smoothest with the mixture screw fully-in. Before it was about 10 turns OUT. The idle speed screw has minimal effect.
An inductive-triggered strobe lamp shows an even firing pattern when clipped an any of the spark plug leads (suggesting they're all firing). The car had a new rotor arm and distributor cap about 3 weeks ago. The HT leads are about a year old (say 3000 miles).
OK, so I think I've ruled out the injection system but still the thing runs like a bag of hammers... until you floor it. Now THAT'S more like it... in fact I'm not sure if it isn't quicker in places. But light throttle cruising is a juddery, bone-shaking experience of clanging diff and loose trim.
So a few things puzzle me:
1. As the car ran reasonably well prior to this work, and ignoring the FI rewire for the moment, how could a simple gasket change cause this? Don't see how it could, unless I introduced air leaks, in which case you'd expect it to run lean. The over-run has more crackles than it's ever had, suggesting lots of unburnt fuel headng straight down the tubes.
2. I am more than competent to rewire a simple electrical circuit like this, before anyone suggests otherwise: I don't think the rewire is the cause. I used wire of at least the same cross-section as original, and chopped 4 feet off the loom length. Now unless the ECU is somehow set-up to work with that length of loom...?
3. When I had similar symptoms on Dexy's car recently, it turned out to be some dry solder joint(s) on the ECU. Whilst not ruling this out, I never removed the ECU from my car during the rewire, and tonight I actually tried driving along with the ECU on the passenger seat, tapping the PCBs with a screwdriver handle. Not a flicker...
4. I suppose I could refit the old water temp sensor.... :clutchingatstraws:
Now this is a bit of a p155er: if I'm struggling with this, how in the hell am I ever going to get it to work properly with a bigger AFM and some fat injectors...
Anyway, here's some porn for you V8 fans...
Ian
Off for an early night...
To carry on from the above, I finished off the injection loom (back to the ECU), leaving it tied with releasable ties just in case.
Anyway, put the plugs back in, topped up the coolant... and it wouldn't start. Oh. eventually I realised that I'd forgotten to reconnect the trigger from the distributor.... doh!
So, with that fixed, I turned the key. What a sack of sh!t. The worst idle I've ever seen on a V8. Remember that one of the symtoms I was hoping to cure was rough idle and poor off-idle response. So now it's even worse. Bizarre.
I went through the entire injection system, checked every colour, every connection, verified that things were where they should be. All OK.
Then I did it again
Now I should add that I've just renewed the inlet manifold gasket and rocker cover gaskets (the former with a composite, the latter with the latest rubber items). There was nothing wrong with te camshaft or followers, and apart from cleaning off old sealant I did nothing else to the engine while it was in bits.
So far I've checked:
Correct connection of fuel pipes to regulator (feed to rail, return from FPR).
Fuel rail pressure - 2.8 bar at idle, reducing with manifold vacuum. Can be adjusted as high as 3.5 bar, at which setting the idle sems to improve... abit.
Response of water temp sensor: fine - the sensor is about a year old. I changed it on the offchance back then, but it made no difference to anything.
Response and correct setting (300mV) of throttle pot. Output rises to just over 4V at full throttle. No evident noise from wiper. With the ignition on, if you 'flick' the throttle open at any part of its range, you can hear the injectors all fire as the ECU thinks you've just nailed it.
Resistances and voltages at airflow meter in accordance with that specified (data from Joolz). Pot response OK, no noise. Temp sensor about 1.2K with AFM hot. Fuel pump switch OK.
All injectors can be triggered by grounding their feed at the ECU connector. Each injector takes about 1.33 - 1.36A.
Water temp sensor, throttle pot, AFM pot and AFM temp sensor can all be measured at the correct pins of the ECU connector.
With the cover off the ECU and the engine running, the ECU 5V rail is correct. You can observe ignition trigger pulses on the PCB, and the output pulses firing the injectors.
You can physically hear and feel the injectors firing.
Ignition timing is about 8 deg BTDC as it always has been while I've had the car.
There is no coolant leakage or any evident air leaks around the inlet manifold, trumpet base or plenum chamber.
There is no cold start injector.
The exhaust gas smells well over-rich. The idle is smoothest with the mixture screw fully-in. Before it was about 10 turns OUT. The idle speed screw has minimal effect.
An inductive-triggered strobe lamp shows an even firing pattern when clipped an any of the spark plug leads (suggesting they're all firing). The car had a new rotor arm and distributor cap about 3 weeks ago. The HT leads are about a year old (say 3000 miles).
OK, so I think I've ruled out the injection system
but still the thing runs like a bag of hammers... until you floor it. Now THAT'S more like it... in fact I'm not sure if it isn't quicker in places. But light throttle cruising is a juddery, bone-shaking experience of clanging diff and loose trim. So a few things puzzle me:
1. As the car ran reasonably well prior to this work, and ignoring the FI rewire for the moment, how could a simple gasket change cause this? Don't see how it could, unless I introduced air leaks, in which case you'd expect it to run lean. The over-run has more crackles than it's ever had, suggesting lots of unburnt fuel headng straight down the tubes.
2. I am more than competent to rewire a simple electrical circuit like this, before anyone suggests otherwise: I don't think the rewire is the cause. I used wire of at least the same cross-section as original, and chopped 4 feet off the loom length. Now unless the ECU is somehow set-up to work with that length of loom...?
3. When I had similar symptoms on Dexy's car recently, it turned out to be some dry solder joint(s) on the ECU. Whilst not ruling this out, I never removed the ECU from my car during the rewire, and tonight I actually tried driving along with the ECU on the passenger seat, tapping the PCBs with a screwdriver handle. Not a flicker...
4. I suppose I could refit the old water temp sensor.... :clutchingatstraws:
Now this is a bit of a p155er: if I'm struggling with this, how in the hell am I ever going to get it to work properly with a bigger AFM and some fat injectors
... Anyway, here's some porn for you V8 fans...
Ian
Off for an early night...
Ian, could it be something to do with the Hydraulic tappets or oil presssure. If the tappets were not pumping up correctly then it could cause some interesting symptoms. If the car has been stood for some time whilst you have been doing the work maybe they have drainned down. Had this problem on a vaxhall engine I rebuilt ran like a bag of nails for a few days then all went OK...... just a thought as you seem to have covered everything else.
I'd say its till worth checking for air leaks with a can of lighter gas sprayed around all the joints post Air flowmeter. The reason is that if it is running lean this can induce a misfire and so allow raw fuel to pass straight through the engine and so mislead you into thinking its too rich. Also have you checked plug condition and lead resistances for the above reason? Also do you have any hesitation when coming on the throttle? As this is also a sign of an air leak. Also check fuel pressure.
Best of luck, this sounds like a knotty one.
Matt
Best of luck, this sounds like a knotty one.
Matt
sevans: It did tap a little on first startup, but it had only been stood for 2 days and soon quietened down. One reason for stripping the top was to check if the cam and followers were OK, 4000 miles on from my DIY rebuild!
matt: I hear what you say. Running out of things to try: in a way I'm hoping an ECU swap reveals the problem - some of the symptoms are very similar to Dexy's car. I'm trying to source some new plugs; they've been in the car at least 10K miles, but they were working fine when I took them out. Leads have been tested and range from about 5K Ohms to 7.5K IIRC depending on length. I suppose they could be breaking down (no stray sparks in the dark though) but again, they were fine only a couple of days before.
Fuel pressure was 2.8 bar, as I've measured it in the past.
Ian
matt: I hear what you say. Running out of things to try: in a way I'm hoping an ECU swap reveals the problem - some of the symptoms are very similar to Dexy's car. I'm trying to source some new plugs; they've been in the car at least 10K miles, but they were working fine when I took them out. Leads have been tested and range from about 5K Ohms to 7.5K IIRC depending on length. I suppose they could be breaking down (no stray sparks in the dark though) but again, they were fine only a couple of days before.
Fuel pressure was 2.8 bar, as I've measured it in the past.
Ian
Ian, My 400SE has had the same symptoms you describe since I got it nearly five years ago. Sometimes much worse than others. I discovered it was due to several different problems. I had introduced air leaks on the small diameter air pipes that run around the top of the engine connecting the plenum to various other valves etc. (not sure what they are called). I have noticed on other engines that these pipes don't generally have clips on them, but adding clips improved the idle slightly. The very small air pipes from the fuel regulator to the plenum and the ignition advance were old and cracked. Replacing them made a bit difference. Magnecor ignition leads helped too. The main culprit turned out to be the air flow meter which a previous owner had 'adjusted'. When I put the car on a rolling road the mixture was so rich at tickover the operator couldn't beleive it. After adjustment it was much better, but basically the air flow meter has had it, even though it passes all the checks you've mentioned. One of the previous owners has altered the spring tension on the flap so it isn't linear any more. I tried a new air flow meter which was great above 2000 rpm but the car wouldn't run below that. It appears the ECU was matched to the air flow meter so I'm fitting an Emerald EMS to finally sort it out. I hope some of this helps.
Leslie
Leslie
Cheers Leslie: don't hear from you on here much! Must get up your way sometime. Do you happen to know if Bob Noble is still around? Must be about 5 years since I last caught up with him at Hartlepool autojumble.
Also, if you haven't binned that airflow meter yet, can I give it a home? I could do with a specimen for dissection...
Right, progress has been made. Neil (Dexy) popped around with his 350 and we proceeded to fiddle. First off we tried my ECU in his car. It ran a shade unevenly, nothing like as bad as my car, but when compared with the sewing machine effect that his own ECU has, quite markedly poor.
Then we dropped his ECU into my car.... and still it ran like a bag of spanners on a Wacker plate.
Now Neil's like me, he throws nowt away, so I wasn't that surprised when he whipped out a box of hardly-used sparkplugs, albeit the standard RV8 spec ones.
When I came to change them, I found that one of my plugs wasn't even hand tight, and realised that my plug socket binds on the cylinder head as the plug goes in. So I checked the rest but they were all tight. Still, it had probably been a contributory factor.
Anyway, in with the 'new' plugs and.... hmmmm. Any difference? Hard to tell.
So there I was, fiddling with the mixture and idle speed, nothing seemed to improve matters but I could easily make them worse. Sure enough the engine slowed down to an almost-stalling chug. And that's when I heard it. The sound of air being sucked in, emanating from somewhere towards the front left of the engine. Note that you could only hear it when the revs dropped this low: once they picked up it was masked. I'd already been around the casting joints with a listening tube, but heard nothing. It seemed to be coming from down in the depths of the valley. Ah, I thought, with a sinking feeling, maybe the new inlet manifold gasket split when I torqued the manifold down. Then the penny dropped....
[TO BE CONTINUED]
[ONLY KIDDING]
Remember the heated throttle body? When I took the heater off, I could see the area of the throttle casting that the water gets to. No way air could get into the intake tract. BUT.... I didn't reckon on the FIXING BOLT HOLES being drilled RIGHT THROUGH into the throttle body!!! AARRGGHH! Only one is a blind hole. One is drilled into the stub for the pipe that draws the fumes from the flame trap, and the other two exit so far inside the plenum chamber that you wouldn't know they were there, until you blow or shine a torch through. Well I'll be buggered. Refitted the bolts from the throttle heater, restarted the car and lo & behold, normal service was resumed. Well almost. Try as I might I couldn't stop the engine from hunting. After fiddling with the fuelling for a while I suggested that we drop my ECU back in so that Neil could get going. We did, and wouldn't you know it, she ran smoothly.
A couple of things have become evident from this: one is that there obviously ARE differences between 4CU ECUs. Neil's car still idles smoother than the 390, though this may be due to the cam, fuel pressure and whatever else is fiddled with on my car. The 390 would hunt like hell on his ECU but smoothed out on mine. The reverse applied to his car.
Another is that it pays to get a second pair of brains on the job, because the more you look, the less you see. So thanks Neil; a mate with the same car is worth his weight in beer ;-)
And thanks to those whose perception of the symptoms was better than mine, even if I did cause the fault myself! I had put the rest of it back together OK... :sheepish:
Now, where's that Jag airflow meter and fat injectors...
Ian
This is DEFINITELY an early night...
>> Edited by wedg1e on Friday 25th July 01:46
Also, if you haven't binned that airflow meter yet, can I give it a home? I could do with a specimen for dissection...
Right, progress has been made. Neil (Dexy) popped around with his 350 and we proceeded to fiddle. First off we tried my ECU in his car. It ran a shade unevenly, nothing like as bad as my car, but when compared with the sewing machine effect that his own ECU has, quite markedly poor.
Then we dropped his ECU into my car.... and still it ran like a bag of spanners on a Wacker plate.
Now Neil's like me, he throws nowt away, so I wasn't that surprised when he whipped out a box of hardly-used sparkplugs, albeit the standard RV8 spec ones.
When I came to change them, I found that one of my plugs wasn't even hand tight, and realised that my plug socket binds on the cylinder head as the plug goes in. So I checked the rest but they were all tight. Still, it had probably been a contributory factor.
Anyway, in with the 'new' plugs and.... hmmmm. Any difference? Hard to tell.
So there I was, fiddling with the mixture and idle speed, nothing seemed to improve matters but I could easily make them worse. Sure enough the engine slowed down to an almost-stalling chug. And that's when I heard it. The sound of air being sucked in, emanating from somewhere towards the front left of the engine. Note that you could only hear it when the revs dropped this low: once they picked up it was masked. I'd already been around the casting joints with a listening tube, but heard nothing. It seemed to be coming from down in the depths of the valley. Ah, I thought, with a sinking feeling, maybe the new inlet manifold gasket split when I torqued the manifold down. Then the penny dropped....
[TO BE CONTINUED]
[ONLY KIDDING]
Remember the heated throttle body? When I took the heater off, I could see the area of the throttle casting that the water gets to. No way air could get into the intake tract. BUT.... I didn't reckon on the FIXING BOLT HOLES being drilled RIGHT THROUGH into the throttle body!!! AARRGGHH! Only one is a blind hole. One is drilled into the stub for the pipe that draws the fumes from the flame trap, and the other two exit so far inside the plenum chamber that you wouldn't know they were there, until you blow or shine a torch through. Well I'll be buggered. Refitted the bolts from the throttle heater, restarted the car and lo & behold, normal service was resumed. Well almost. Try as I might I couldn't stop the engine from hunting. After fiddling with the fuelling for a while I suggested that we drop my ECU back in so that Neil could get going. We did, and wouldn't you know it, she ran smoothly.
A couple of things have become evident from this: one is that there obviously ARE differences between 4CU ECUs. Neil's car still idles smoother than the 390, though this may be due to the cam, fuel pressure and whatever else is fiddled with on my car. The 390 would hunt like hell on his ECU but smoothed out on mine. The reverse applied to his car.
Another is that it pays to get a second pair of brains on the job, because the more you look, the less you see. So thanks Neil; a mate with the same car is worth his weight in beer ;-)
And thanks to those whose perception of the symptoms was better than mine, even if I did cause the fault myself! I had put the rest of it back together OK... :sheepish:
Now, where's that Jag airflow meter and fat injectors...
Ian
This is DEFINITELY an early night...
>> Edited by wedg1e on Friday 25th July 01:46
WEll done for tracking it down, just for future info this is my method for inding air leaks:
1) obtain a can of butane lighter gas and fit with a short length of hose and a flattened bit of pipe in the end to provide a nozzle.
2) With engine running and leaned out if possible spray lighter gas around each and every joint , dodgy hose etc after the airflow meter.
3) If the engine picks up / revs then its pulling the 'fuel' and you've found your leak.
Don't worry about leaving lots of fuel around as this stuff evaporates v. quickly and requires a spark to set it off, hot exhaust won't do it.
Matt
1) obtain a can of butane lighter gas and fit with a short length of hose and a flattened bit of pipe in the end to provide a nozzle.
2) With engine running and leaned out if possible spray lighter gas around each and every joint , dodgy hose etc after the airflow meter.
3) If the engine picks up / revs then its pulling the 'fuel' and you've found your leak.
Don't worry about leaving lots of fuel around as this stuff evaporates v. quickly and requires a spark to set it off, hot exhaust won't do it.
Matt
350matt said:
WEll done for tracking it down, just for future info this is my method for inding air leaks:
1) obtain a can of butane lighter gas and fit with a short length of hose and a flattened bit of pipe in the end to provide a nozzle.
2) With engine running and leaned out if possible spray lighter gas around each and every joint , dodgy hose etc after the airflow meter.
3) If the engine picks up / revs then its pulling the 'fuel' and you've found your leak.
Don't worry about leaving lots of fuel around as this stuff evaporates v. quickly and requires a spark to set it off, hot exhaust won't do it.
Matt
I did try similar techniques, just didn't try UNDERNEATH the throttle body!
Ian
gaz666 said:
The best read ive had for ages, very entertaining, when does the film come out?
Cheers, I do my best!
I suppose on film you could catch the hair-tearing, foot-stamping, door-slamming, spanner-throwing, beer-swigging and computer-bashing that accompanies the actual work... Neil:
Seemed to go alright, but I don't seem to be able to shake off that pesky cream 350. No point in a V8 if all the power is above 5500 rpm...
Ian
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