Main relay location
Discussion
Hi,
I'm still playing with electrical gizmos on my 350I : test #15 ("resistance of injector circuit", Wedges Epistles, Page 22) request to find the main electrical relay, but how to identify this specific relay, and where is it located (behind the ECU, as the others ?) ?
Injector #1 seems to not working anymore, this is the last of the tests to follow before an injector swap.
Thanks for your help,
Chris
I'm still playing with electrical gizmos on my 350I : test #15 ("resistance of injector circuit", Wedges Epistles, Page 22) request to find the main electrical relay, but how to identify this specific relay, and where is it located (behind the ECU, as the others ?) ?
Injector #1 seems to not working anymore, this is the last of the tests to follow before an injector swap.
Thanks for your help,
Chris
Sounds like you may have a break in a wire, the injectors fire all four Injectors per bank. So if 3, 5 and 7 are working and 1 is not then there may well be a wire break, or bad earth?
Check all wires at the back of the cylinder head.
Check pin 15 I think from the ECU connector to the Injector #1 plug for continuity.
May also want to also check the power resistor too.
Check all wires at the back of the cylinder head.
Check pin 15 I think from the ECU connector to the Injector #1 plug for continuity.
May also want to also check the power resistor too.
Edited by BlueWedgy on Monday 23 March 20:21
Edited by BlueWedgy on Monday 23 March 20:21
Hi,
Thanks for your message BW.
I've already checked the power resistor, compare the #1 injector resitance to the others, and checked the continuity between the power resistor and the injector (Yellow/narrow green stripe if my memory is good), everything seems to be correct.
I also checked each connections and pins on the ECU side, all was fine, but hadn't checked the earth yet.
This afternoon, I made a fuel feed with a T pipe from the cold start injector hose to feed a spare injector connected to #1 injector plug, it was perfectly spraying in a small jarr.
One I get this result, I swapped the tested spare injector for the -apparently- not working one, but the problem is the same.
So, it's not the injector itself.
I'll check the continuity from the ECU connector to the Injector #1 plug, good idea.
No idea about the location of this so called "main relay" ? It seems that the resistance value of each wire is crucial in this injection system.
Thanks for your message BW.
I've already checked the power resistor, compare the #1 injector resitance to the others, and checked the continuity between the power resistor and the injector (Yellow/narrow green stripe if my memory is good), everything seems to be correct.
I also checked each connections and pins on the ECU side, all was fine, but hadn't checked the earth yet.
This afternoon, I made a fuel feed with a T pipe from the cold start injector hose to feed a spare injector connected to #1 injector plug, it was perfectly spraying in a small jarr.
One I get this result, I swapped the tested spare injector for the -apparently- not working one, but the problem is the same.
So, it's not the injector itself.
I'll check the continuity from the ECU connector to the Injector #1 plug, good idea.
No idea about the location of this so called "main relay" ? It seems that the resistance value of each wire is crucial in this injection system.
Presumably rather than checking the resistance from the ECU to the relay, you could check the resistance from the ECU to pins 2 and 9 of the Power resistors which should give the same readings.
The relay will be one of them on the relay board behind the ECU. To be honest my relay layout doesn't tie up with anything I've ever seen online, so hard to say which position the relay will be in, but on mine there are 2 relays marked 'ignition' so probably one of those.
Those tests are really good for finding injection faults, I found a few bad connections on mine and also found a couple of bad joins buried in the looms.
Problems I had was also bad earth connections to the ECU and bad connections on the relay board (some relays getting really hot).
Hope that helps - good luck...
The relay will be one of them on the relay board behind the ECU. To be honest my relay layout doesn't tie up with anything I've ever seen online, so hard to say which position the relay will be in, but on mine there are 2 relays marked 'ignition' so probably one of those.
Those tests are really good for finding injection faults, I found a few bad connections on mine and also found a couple of bad joins buried in the looms.
Problems I had was also bad earth connections to the ECU and bad connections on the relay board (some relays getting really hot).
Hope that helps - good luck...
The 2-pin injector connectors are prone to suffering from the contact 'fingers' getting bent out of shape due to rough handling... so everything can appear to measure OK but still not be connected. The way to check is to measure from the ECU connector with the injectors plugged in one at a time. Have a good peer into the connector bodies and see if the fingers look in good order.
You can buy replacement fingers and bodies from Vehicle Wiring Products and elsewhere.
By the 'main' relay I presume you mean the injection system main relay; it's usually mounted adjacent to the red Pektron steering module, the wiring colours are given on the usual diagrams.
There are also usually two 'main' or power relays, switched by the ignition, which power the other electrics. It's something of a compromise as even though they're claimed to be good for 30A they can still die from overcurrent loads - people adding accessories don't bother to check what else is being powered from either relay.
Modern cars have much beefier relays, 50A plus, though they won't usually fit the same sockets as on the Wedges, so not an easy upgrade but maybe worth pursuing if done tidily.
You can buy replacement fingers and bodies from Vehicle Wiring Products and elsewhere.
By the 'main' relay I presume you mean the injection system main relay; it's usually mounted adjacent to the red Pektron steering module, the wiring colours are given on the usual diagrams.
There are also usually two 'main' or power relays, switched by the ignition, which power the other electrics. It's something of a compromise as even though they're claimed to be good for 30A they can still die from overcurrent loads - people adding accessories don't bother to check what else is being powered from either relay.
Modern cars have much beefier relays, 50A plus, though they won't usually fit the same sockets as on the Wedges, so not an easy upgrade but maybe worth pursuing if done tidily.
Hi Wedg1e, I used the cold start injector fuel hose to feed a spare injector I have, and connected it to the -apparently- not working injector connector : it sprayed fuel perfectly.
I might have been wrong at thinking it should proove that the problem do not come from this conector ?
Whatever, I'll do all the tests recommended here, starting by the ones about potential bad earth connections.
I might have been wrong at thinking it should proove that the problem do not come from this conector ?
Whatever, I'll do all the tests recommended here, starting by the ones about potential bad earth connections.
chris59 said:
Hi Wedg1e, I used the cold start injector fuel hose to feed a spare injector I have, and connected it to the -apparently- not working injector connector : it sprayed fuel perfectly.
I might have been wrong at thinking it should proove that the problem do not come from this conector ?
Whatever, I'll do all the tests recommended here, starting by the ones about potential bad earth connections.
Hmm, sorry, maybe I misunderstood what you'd tried so far. You put a spare injector in place of #1 and fed it fuel from the cold start feed and it appeared to work? That proves the spare injector works and it was making contact with the 2-pin connector. It doesn't necessarily mean that when you plug the connector back into #1 that it is making contact. In theory it ought to be, but then in theory, theory and practice are the same. In practice they often aren't I might have been wrong at thinking it should proove that the problem do not come from this conector ?
Whatever, I'll do all the tests recommended here, starting by the ones about potential bad earth connections.
The injectors are prone to sticking closed if not used for a while; a good clouting on the steel body with a suitable tool (brass drift and a small hammer will do) and repeatedly turning the injector feed on and off often unsticks them - with ignition on, repeatedly flicking the throttle open and closed to trigger the accelerator pump response is a good way to pulse the injector feed (with the other 7 unplugged or you'll flood the inlet). You'll clearly hear it ticking if it is firing.
I think this is getting a bit messy, as to the original fault, if any, cause and effect?
As per Wedge1e, people can sometimes read things in different ways.
Q. Apart from running through a test procedure and what appears on the surface and not fully being able to follow it and the location of a certain relay, what are your full sympton/s. Not starting, poor running? nothing just testing?
If you want to test the Injector, then 2 AA batteries in series 3V (do not use 12V) will test the Injector it will or should audibly click?
Quick test for spray use some easy start of brake cleaner attached to the hose section, whilst testing.
Some time ago Wedge1e kindly sent me a spare Injector, that on the surface worked on the bench, but was intermittent when installed in the car, this when being asked to fire at pace (engine running).
If you want to test the harness wiring to the Injector then a Noid tester will test this, no real need to buy this, any old LED and suitable resister will effect the same result. Whilst cranking the LED should blink.
This is discussed here a bit:
https://www.pistonheads.com/gassing/topic.asp?h=0&...
As per Wedge1e, people can sometimes read things in different ways.
Q. Apart from running through a test procedure and what appears on the surface and not fully being able to follow it and the location of a certain relay, what are your full sympton/s. Not starting, poor running? nothing just testing?
If you want to test the Injector, then 2 AA batteries in series 3V (do not use 12V) will test the Injector it will or should audibly click?
Quick test for spray use some easy start of brake cleaner attached to the hose section, whilst testing.
Some time ago Wedge1e kindly sent me a spare Injector, that on the surface worked on the bench, but was intermittent when installed in the car, this when being asked to fire at pace (engine running).
If you want to test the harness wiring to the Injector then a Noid tester will test this, no real need to buy this, any old LED and suitable resister will effect the same result. Whilst cranking the LED should blink.
This is discussed here a bit:
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Hello guys,
I also swapped the "flying" spare injector for the -apparently- not working one.
The result is that, when the engine is cold, fuel "over" feed by the cold start injector, ALL the cylinders are working : if I unplug the #1 spark plus lead, I can hear the difference.
After a moment, the engine is warm enough, so cold start injector stop : #1 cylinder stop working immediatly.
While the engine is running, I can disconnect the injector or spark plug, there is no difference, this cylinder don't work (sorry for my poor explanations, English is not my native language !).
I also swapped the "flying" spare injector for the -apparently- not working one.
The result is that, when the engine is cold, fuel "over" feed by the cold start injector, ALL the cylinders are working : if I unplug the #1 spark plus lead, I can hear the difference.
After a moment, the engine is warm enough, so cold start injector stop : #1 cylinder stop working immediatly.
While the engine is running, I can disconnect the injector or spark plug, there is no difference, this cylinder don't work (sorry for my poor explanations, English is not my native language !).
Hi,
It is not uncommon to remove the cold start injector, by just removing the connector and securing it with a cable tye. I have run my car like this for 4-5 years.
I assume you have confirmed spark at the spark plug? It has been known that the spark plug lead routing can cause mis-fire issues.
It is suggested that you start the car at night (dark) to ensure that no arking of the ignition system is present.
Have you carried out a compression test?
I was having issues and found the Camshaft to be worn on both number 1 lobes, I have recently (last couple of weeks) replaced it with a new one. It is said that a cam will likely be worn at 85K miles, this proved so for me, although I have no idea of the true mileage of the Cam that I replaced.
Is the fuel pressure to specification, when running?
Confirm that you have an Injector pulse at the number 1 harness connector, as per the previous post.
When I thought I had Injector issues I left the injector in the inlet and connected the spare Injector to the fuel rail ith a length of hose, then placed It inside a small drink bottle to observe the spray pattern.
Have you checked the sensors in the top of the block are within range?
Air leaks cause all sorts of issues, a common failure is the Plenum to AFR hose.
Sorry if all this seems obvious, it just the process I went through for a fair while with mine.
It turned out to be a spark plug breaking down, I then made it worse by purchasing fake new spark plugs, adding to the mix. An Impedence check showed the fault.
All the best.
It is not uncommon to remove the cold start injector, by just removing the connector and securing it with a cable tye. I have run my car like this for 4-5 years.
I assume you have confirmed spark at the spark plug? It has been known that the spark plug lead routing can cause mis-fire issues.
It is suggested that you start the car at night (dark) to ensure that no arking of the ignition system is present.
Have you carried out a compression test?
I was having issues and found the Camshaft to be worn on both number 1 lobes, I have recently (last couple of weeks) replaced it with a new one. It is said that a cam will likely be worn at 85K miles, this proved so for me, although I have no idea of the true mileage of the Cam that I replaced.
Is the fuel pressure to specification, when running?
Confirm that you have an Injector pulse at the number 1 harness connector, as per the previous post.
When I thought I had Injector issues I left the injector in the inlet and connected the spare Injector to the fuel rail ith a length of hose, then placed It inside a small drink bottle to observe the spray pattern.
Have you checked the sensors in the top of the block are within range?
Air leaks cause all sorts of issues, a common failure is the Plenum to AFR hose.
Sorry if all this seems obvious, it just the process I went through for a fair while with mine.
It turned out to be a spark plug breaking down, I then made it worse by purchasing fake new spark plugs, adding to the mix. An Impedence check showed the fault.
All the best.
Edited by BlueWedgy on Friday 27th March 06:50
Hi BW, replies in,your text 
:
I assume you have confirmed spark at the spark plug? Yes, either with a new one or the actual one who's nearly new
It has been known that the spark plug lead routing can cause mis-fire issues.
It is suggested that you start the car at night (dark) to ensure that no arking of the ignition system is present. ALL the wires are new, 8mm ones
Have you carried out a compression test? Yes, same compression on all cylinders
Is the fuel pressure to specification, when running? I'll check today, hopefully
Confirm that you have an Injector pulse at the number 1 harness connector, as per the previous post.:
When I thought I had Injector issues I left the injector in the inlet and connected the spare Injector to the fuel rail ith a length of hose, then placed It inside a small drink bottle to observe the spray pattern. That's what I've done, by connecting a length of hose to the cold start injector feed with a "T"
Have you checked the sensors in the top of the block are within range ? Where can I get their values ?
Air leaks cause all sorts of issues, a common failure is the Plenum to AFR hose. I've already checked air leaks with a brake cleaner spray, no result.
Sorry if all this seems obvious, it just the process I went through for a fair while with mine. No problem, you're very helpfull
: I assume you have confirmed spark at the spark plug? Yes, either with a new one or the actual one who's nearly new
It has been known that the spark plug lead routing can cause mis-fire issues.
It is suggested that you start the car at night (dark) to ensure that no arking of the ignition system is present. ALL the wires are new, 8mm ones
Have you carried out a compression test? Yes, same compression on all cylinders
Is the fuel pressure to specification, when running? I'll check today, hopefully
Confirm that you have an Injector pulse at the number 1 harness connector, as per the previous post.:
When I thought I had Injector issues I left the injector in the inlet and connected the spare Injector to the fuel rail ith a length of hose, then placed It inside a small drink bottle to observe the spray pattern. That's what I've done, by connecting a length of hose to the cold start injector feed with a "T"
Have you checked the sensors in the top of the block are within range ? Where can I get their values ?
Air leaks cause all sorts of issues, a common failure is the Plenum to AFR hose. I've already checked air leaks with a brake cleaner spray, no result.
Sorry if all this seems obvious, it just the process I went through for a fair while with mine. No problem, you're very helpfull
Edited by chris59 on Friday 27th March 09:46
Edited by chris59 on Friday 27th March 09:47
UPDATE :
I made a simple test this morning : I started the engine, run on 8 cylinders, cold start injector doing its job as usually, disconnected #1 spark plug, it made a real difference, the engine shown immediatly it has lost this cylinder.
Once the cold start injector cut out, #1 cylinder stop working, the engine run on 7 cylinders : I can disconnect spark plug #1, it make no difference.
I made a simple test this morning : I started the engine, run on 8 cylinders, cold start injector doing its job as usually, disconnected #1 spark plug, it made a real difference, the engine shown immediatly it has lost this cylinder.
Once the cold start injector cut out, #1 cylinder stop working, the engine run on 7 cylinders : I can disconnect spark plug #1, it make no difference.
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