350i Starting Problems

350i Starting Problems

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Benjamico

Original Poster:

25 posts

212 months

Friday 18th April 2014
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I recently bought a slightly delapidated 350i with a friend with the hope of getting it on the road ready for Le Mans this year, it had a replacement engine in place but not wired or plumbed.

We have now installed all the ancillaries and wired it up as best we can, however we can't get it to start.

We have checked the spark and it is strong, we have also checked the fuel is being delivered and (after a little head scratching and re-wiring) the fuel pump is working as it should be.

We think that either we have the timing out of sync or the fuel injectors possibly aren't firing correctly. We used a noid light and there seems to be a (possibly weak) pulse on each fuel injector, it also appears that the injectors are firing too rapidly in comparison to the spark plugs.

As we are starting to run out of time, are there any obvious things we may be missing or are there any TVR specialists anybody can reccomend in the Hertfordshire area? Happy to pay for their time if they have the ability to diagnose the problem.

Any help or info would be very much appreciated.

Thanks

Ben




adam quantrill

11,535 posts

241 months

Friday 18th April 2014
quotequote all
Benjamico said:
We think that either we have the timing out of sync or the fuel injectors possibly aren't firing correctly. We used a noid light and there seems to be a (possibly weak) pulse on each fuel injector, it also appears that the injectors are firing too rapidly in comparison to the spark plugs.
The injectors should have quite a strong pulse - I have had LED's attached to mine (from +ve to injector) and they were very bright.

They also alternate while cranking - it's a very distinctive pattern - left, right, left, right, twice a second. Don't forget they are in banks so all left ones fire at the same time, then all right, and repeat.

Spark, fuel pressure, fuel, air. That's all you need!

Benjamico

Original Poster:

25 posts

212 months

Friday 18th April 2014
quotequote all
Thanks Adam, that explains the firing pattern we saw, however the light was extremely dull.

Silly question possibly, but when checking continuity of earth, we found no earth on either side of the conector of each injector, do you know if this is this normal?

Thanks again

V8 Fettler

7,019 posts

131 months

Saturday 19th April 2014
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The ECU earths the injectors to fire them, do you have a wiring diagram? Are the plugs soaking wet with petrol or dry?

Benjamico

Original Poster:

25 posts

212 months

Saturday 19th April 2014
quotequote all
Thanks Fettler, plugs were dry, so I'm guessing the signal must be too weak to fire the injectors.

I've got some RV8 Efi drawings from doing a google image search.

When searching, I've seen a few references to a resistor in the coil wiring, I haven't seen a resistor and wonder if this could be partly responsible?

adam quantrill

11,535 posts

241 months

Saturday 19th April 2014
quotequote all
Yeah the return path is to the ECU but did you connect the resistor pack (it goes through this too)?

To test if the injectors are firing:

a) Ignition on
b) twist throttle through 45-90 degrees quite quick

You should hear a "click" from all 8 injectors - this is the "enrichment" pulse.

V8 Fettler

7,019 posts

131 months

Saturday 19th April 2014
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From HJ2's vintagemodelairplane website:



Bottom right shows power resistors, should be 12V here, ECU earths the other side of the injector coils to open the injectors.

Terminal 1 into the ECU is worth monitoring (from ignition amp), I've never seen the trigger resistor on my 350i, it might exist but I've never had cause to look for it.

Benjamico

Original Poster:

25 posts

212 months

Sunday 4th May 2014
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Thank you both.

Adam, I've just been out and tried your suggestion with the throttle twist. It did indeed cause the injectors to click, but when I pulled out a spark plug and it was still dry.

The fuel pump is definitely delivering fuel so I'm pretty stumped!

mrzigazaga

18,534 posts

164 months

Sunday 4th May 2014
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Are you definitely getting fuel up to the injectors?..

350zwelgje

1,818 posts

260 months

Sunday 4th May 2014
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You probably have, but can check if the fuel pressure regulator is after the injectors/at the end of the fuel rail (not before or the entry of it). Or even feed and return line connected to the right points of the fuel rail/fuel pressure regulator.

More people have had issues with the fuel pump: provide power and it works, connected to the normal wiring it doesn't work. You can try to run two extra wires direct from the battery, when the pump is running then try to start the engine to exclude the normal wiring & setup.

Rob

Benjamico

Original Poster:

25 posts

212 months

Sunday 4th May 2014
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Thanks, I just double checked by pulling the main fuel hose off and it is definitely pumping a good quantity through it.


Wedg1e

26,760 posts

264 months

Monday 5th May 2014
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350zwelgje said:
check if the ... feed and return line connected to the right points of the fuel rail/fuel pressure regulator.
This. I've seen them installed the wrong way round - and even done it myself paperbag
Results in no rail pressure.

Benjamico

Original Poster:

25 posts

212 months

Monday 5th May 2014
quotequote all
350zwelgje said:
You probably have, but can check if the fuel pressure regulator is after the injectors/at the end of the fuel rail (not before or the entry of it). Or even feed and return line connected to the right points of the fuel rail/fuel pressure regulator.

More people have had issues with the fuel pump: provide power and it works, connected to the normal wiring it doesn't work. You can try to run two extra wires direct from the battery, when the pump is running then try to start the engine to exclude the normal wiring & setup.

Rob
I don't think my brain was in gear when I first read this, I've now caught up!

The return feed is connected to the FPR with the delivery hose connected directly to the rail.

I pulled off the return feed hose and tried starting it with the return blocked in case the FPR is stuck open but no luck!

Benjamico

Original Poster:

25 posts

212 months

Wednesday 14th May 2014
quotequote all
I spent a bit more time with the wiring diagram and a multimeter this evening, I'm now pretty convinced it is the injectors not getting a strong enough signal.

I put a noid light between the yellow +ve wire of the injector harness and a good earth and the light came on very brightly. When I cranked the engine and put the light between the two terminals of the injector plug it gave a really really dull pulse.

I have checked all the earths to the ECU and all seem OK, do the symptoms correlate to any known issues with the wedge?

Thanks


adam quantrill

11,535 posts

241 months

Wednesday 14th May 2014
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Have you tried the rotate throttle and click test I mentioned above? If they don't click that will double-check the theory.

The circuit returns through the power resistors so the most likely scenario is the single brown/orange wire is not connected all the way through or the relays aren't working. THis will kill both banks. If one bank is working and one isn't, then the best bet is the ECU power transistors for that bank.

If the click test causes obvious clicking then change tach (geddit?) and make sure the ignition pulses are getting to the ECU to tell it to fire at all.

Benjamico

Original Poster:

25 posts

212 months

Wednesday 14th May 2014
quotequote all
adam quantrill said:
Have you tried the rotate throttle and click test I mentioned above? If they don't click that will double-check the theory.

The circuit returns through the power resistors so the most likely scenario is the single brown/orange wire is not connected all the way through or the relays aren't working. THis will kill both banks. If one bank is working and one isn't, then the best bet is the ECU power transistors for that bank.

If the click test causes obvious clicking then change tach (geddit?) and make sure the ignition pulses are getting to the ECU to tell it to fire at all.
I tried the click test and it does click on both banks, there is still no fuel delivery into the cylinder though, it's very strange!

I have also tried removing the distributor and spinning the shaft, this also genegates clicks but again no fuel delivery. There is really good fuel pressure at the rail too... very confusing!

Maybe I do need to change tach... has anybody got a box of matches they can lend me?! biggrin

Wedg1e

26,760 posts

264 months

Wednesday 14th May 2014
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Is the cold start injector fitted and connected? If so you should be able to remove it from the plenum, direct it into a jar and crank the engine, during which time it should spray into the jar.
If it does then the engine should at least try to fire; that would suggest the ignition system is doing what it should and prove there is at least some rail pressure.
The usual issue with RV8s that have been stood is that the injectors sieze up but if you're definitely hearing them click when the throttle is flicked that would suggest otherwise - I've seen 6 out of 8 stuck closed before now but even that engine was trying to start.

You could try the old trick of throwing a couple of capfuls of fuel through the throttle plate (with it open of course), refit the air hose and crank the engine; if it at least coughs a few times you know the fuelling is the issue. It could be as daft as all 8 injectors are firing, the rail pressure is adequate but the injector inlets are blocked.

Next stage I'd say is to whip the plenum chamber and trumpet base off, lift the injector rail and see if any of the injectors pass any fuel at all when triggered; your 'noid light; is probably confusing the issue because firstly the injectors don't see a straight 12v, they're fed from the resistor pack and earthed (to fire them) by the ECU transistors. The pulse is so short that a filament lamp won't have time to reach full brightness so will appear dim.

A point to check is that the injection system earths are in good order; there should be two black wires (one thicker than the other) going to ring terminals on a stud on the rear of the lefthand cylinder head. The mating surfaces of the head, the rings, the stud and any nuts should be bright and shiny. The engine also needs a good earth to the battery.

As General Patton once allegedly said: Go down that road until you get blown up, then report back biggrin

MrPicky

1,233 posts

266 months

Thursday 15th May 2014
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Have you tried disconnecting and reconnecting the injector resistor pack on the front wing, your investigation shows low injector volts so this connection (which often corrodes a bit) could be at fault.

If this proves to be the case then a bit of vaseiline on the pins should prevent a bit of corrosion.

Russ


simonwedge

743 posts

179 months

Thursday 15th May 2014
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If you're coming to the end of your tether you could try taking it to a classic Land Rover/Range Rover specialist, if you've got one nearby?

adam quantrill

11,535 posts

241 months

Thursday 15th May 2014
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I think Ian is getting to the nub - the injectors are clicking so the drive voltage is adequate and you have also debugged the dizzy rotation/clicking so the trigger pulses are getting to the ECU.

Each injector has a little fuel filter basket (correct me if I am wrong) maybe they are gunged up? The "cold start" injector test sounds work doing and here's a twist on that: after about 10 seconds the cold start should turn off, then disconnect the electrical feed to the injector and borrow one from cylinder 4 or 6 injector.

If it is now pulsing fuel when you crank it, that confirms the ECU, resistor pack, dizzy, pressure etc are all OK.

If the other injectors have blockages it's probably because they pass much more fuel, the cold start one is only on briefly.

Edited by adam quantrill on Thursday 15th May 18:30