The Official Fuel Injector Thread
12-28-2007, 09:29 PM
#16
Rennlist Member
H...........stating the obvious here; there's 9 53B relays...........if he horn blows and the HVAC works theres 4 you can swap around with the FP and LH
12-28-2007, 09:35 PM
#17
Race Car
its an easy test for the harness... disconnect the battery, and unplug both ecu's.
disconnect each injector plug and check for continuity between both wires on the injector plug... if any one of them are shorted they will all show continuity.
__________________
If you test it this way you will see a short, the Inj coils will show a low resistance. I had the same issue after a intake rebuild found 2 shorted connectors on the Inj. If your getting noware removing all the Inj connectors, Ecm connectors and check for a short on the connectors. You may also check each Inj's ohms for a short, I believe it should be 17 ohms.
I think this is not your problem, but a way to check Inj shorts if you run out of things to drive you crazy.
Sterling
Cognac 1990 928S4 5spd, 6.4 liter w/VarioCam
Custom Paul Champagne Interior
Koni/Eibach, GTS brakes
GTS Quarterpanels & no side moldings
Fikse Wheels
disconnect each injector plug and check for continuity between both wires on the injector plug... if any one of them are shorted they will all show continuity.
__________________
If you test it this way you will see a short, the Inj coils will show a low resistance. I had the same issue after a intake rebuild found 2 shorted connectors on the Inj. If your getting noware removing all the Inj connectors, Ecm connectors and check for a short on the connectors. You may also check each Inj's ohms for a short, I believe it should be 17 ohms.
I think this is not your problem, but a way to check Inj shorts if you run out of things to drive you crazy.
Sterling
Cognac 1990 928S4 5spd, 6.4 liter w/VarioCam
Custom Paul Champagne Interior
Koni/Eibach, GTS brakes
GTS Quarterpanels & no side moldings
Fikse Wheels
12-28-2007, 11:50 PM
#19
Supercharged
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H--
Replace the FP relay and the LH realy with known good. The fact that the relay clicks just means it's "trying". Doesn't guarantee results. The 53B relays are too cheap to take a chance on, IMHO.
You can check the wiring harness from the protection relay socket by the LH brain, and at the brain connector itself. This is likely easier and faster than pulling fuel rail covers and risking more damage to crispy wiring under the hood.
The wiring diagram suggests that power for the circuit is applied to all injectors through the fuel pump relay, which receives battery power directly through a dedicated feed from the battery. Means it's one of the several smaller cables that attach to the battery positive terminal. Been in the battery well lately? If that feeder is disturbed, the FP relay may click but no power to MFI or the fuel pump. Is the pump running? The FP relay shares supply power with the MFI relay contact which feeds the LH module itself (via W23 ce connector to pin 9 on the LH connector). LH feeds power to the injectors via pin 18 in the connector. With the connector removed, you should test from 18 in the connector to ground and see an open circuit. If anything less, there's a fault to ground someplace in the injector wiring or in the ignition protection relay itself. Pull the relay aftre this test to be sure, since you'll want to do the next test there anyway.
The other side of the injectors is split between 1-4-6-7, and 2-3-5-8 at the monitoring relay. Pull that relay, and test from pin 5 on the relay socket to pin 18 on the LH connector. The resistance may be somewhere north of a few ohms, but not a dead short. Test from pin 2 in the relay socket to pin 18 at the LH connector, and the resistance should be the same as you measured from pin 5 previously. If one of these is less (closer to zero or actually zero ohms) you have at least isolated the problem to one set. If pin 5 is low, look at injector connectors 1-4-6-7; If pin 2 is way low, look at 2-3-5-8 connectors for shorted wiring.
If still no injection after these tests, poost back and we'll dig deeper.
Replace the FP relay and the LH realy with known good. The fact that the relay clicks just means it's "trying". Doesn't guarantee results. The 53B relays are too cheap to take a chance on, IMHO.
You can check the wiring harness from the protection relay socket by the LH brain, and at the brain connector itself. This is likely easier and faster than pulling fuel rail covers and risking more damage to crispy wiring under the hood.
The wiring diagram suggests that power for the circuit is applied to all injectors through the fuel pump relay, which receives battery power directly through a dedicated feed from the battery. Means it's one of the several smaller cables that attach to the battery positive terminal. Been in the battery well lately? If that feeder is disturbed, the FP relay may click but no power to MFI or the fuel pump. Is the pump running? The FP relay shares supply power with the MFI relay contact which feeds the LH module itself (via W23 ce connector to pin 9 on the LH connector). LH feeds power to the injectors via pin 18 in the connector. With the connector removed, you should test from 18 in the connector to ground and see an open circuit. If anything less, there's a fault to ground someplace in the injector wiring or in the ignition protection relay itself. Pull the relay aftre this test to be sure, since you'll want to do the next test there anyway.
The other side of the injectors is split between 1-4-6-7, and 2-3-5-8 at the monitoring relay. Pull that relay, and test from pin 5 on the relay socket to pin 18 on the LH connector. The resistance may be somewhere north of a few ohms, but not a dead short. Test from pin 2 in the relay socket to pin 18 at the LH connector, and the resistance should be the same as you measured from pin 5 previously. If one of these is less (closer to zero or actually zero ohms) you have at least isolated the problem to one set. If pin 5 is low, look at injector connectors 1-4-6-7; If pin 2 is way low, look at 2-3-5-8 connectors for shorted wiring.
If still no injection after these tests, poost back and we'll dig deeper.
12-29-2007, 12:10 AM
#20
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(me and John Davis working on Heinrich's car in John's garage...)
on the monitoring relay connector:
pin 5: 4.5 ohms
pin 2: .5 ohms
injectors 2,3 and 8 all showed 16 ohms, injector 5 was .5 ohms.
found cyl 5 injector connector wires frayed and shorted together.
separated and wrapped wires - car starts right up...
dave
on the monitoring relay connector:
pin 5: 4.5 ohms
pin 2: .5 ohms
injectors 2,3 and 8 all showed 16 ohms, injector 5 was .5 ohms.
found cyl 5 injector connector wires frayed and shorted together.
separated and wrapped wires - car starts right up...
dave
H--
Replace the FP relay and the LH realy with known good. The fact that the relay clicks just means it's "trying". Doesn't guarantee results. The 53B relays are too cheap to take a chance on, IMHO.
You can check the wiring harness from the protection relay socket by the LH brain, and at the brain connector itself. This is likely easier and faster than pulling fuel rail covers and risking more damage to crispy wiring under the hood.
The wiring diagram suggests that power for the circuit is applied to all injectors through the fuel pump relay, which receives battery power directly through a dedicated feed from the battery. Means it's one of the several smaller cables that attach to the battery positive terminal. Been in the battery well lately? If that feeder is disturbed, the FP relay may click but no power to MFI or the fuel pump. Is the pump running? The FP relay shares supply power with the MFI relay contact which feeds the LH module itself (via W23 ce connector to pin 9 on the LH connector). LH feeds power to the injectors via pin 18 in the connector. With the connector removed, you should test from 18 in the connector to ground and see an open circuit. If anything less, there's a fault to ground someplace in the injector wiring or in the ignition protection relay itself. Pull the relay aftre this test to be sure, since you'll want to do the next test there anyway.
The other side of the injectors is split between 1-4-6-7, and 2-3-5-8 at the monitoring relay. Pull that relay, and test from pin 5 on the relay socket to pin 18 on the LH connector. The resistance may be somewhere north of a few ohms, but not a dead short. Test from pin 2 in the relay socket to pin 18 at the LH connector, and the resistance should be the same as you measured from pin 5 previously. If one of these is less (closer to zero or actually zero ohms) you have at least isolated the problem to one set. If pin 5 is low, look at injector connectors 1-4-6-7; If pin 2 is way low, look at 2-3-5-8 connectors for shorted wiring.
If still no injection after these tests, poost back and we'll dig deeper.
Replace the FP relay and the LH realy with known good. The fact that the relay clicks just means it's "trying". Doesn't guarantee results. The 53B relays are too cheap to take a chance on, IMHO.
You can check the wiring harness from the protection relay socket by the LH brain, and at the brain connector itself. This is likely easier and faster than pulling fuel rail covers and risking more damage to crispy wiring under the hood.
The wiring diagram suggests that power for the circuit is applied to all injectors through the fuel pump relay, which receives battery power directly through a dedicated feed from the battery. Means it's one of the several smaller cables that attach to the battery positive terminal. Been in the battery well lately? If that feeder is disturbed, the FP relay may click but no power to MFI or the fuel pump. Is the pump running? The FP relay shares supply power with the MFI relay contact which feeds the LH module itself (via W23 ce connector to pin 9 on the LH connector). LH feeds power to the injectors via pin 18 in the connector. With the connector removed, you should test from 18 in the connector to ground and see an open circuit. If anything less, there's a fault to ground someplace in the injector wiring or in the ignition protection relay itself. Pull the relay aftre this test to be sure, since you'll want to do the next test there anyway.
The other side of the injectors is split between 1-4-6-7, and 2-3-5-8 at the monitoring relay. Pull that relay, and test from pin 5 on the relay socket to pin 18 on the LH connector. The resistance may be somewhere north of a few ohms, but not a dead short. Test from pin 2 in the relay socket to pin 18 at the LH connector, and the resistance should be the same as you measured from pin 5 previously. If one of these is less (closer to zero or actually zero ohms) you have at least isolated the problem to one set. If pin 5 is low, look at injector connectors 1-4-6-7; If pin 2 is way low, look at 2-3-5-8 connectors for shorted wiring.
If still no injection after these tests, poost back and we'll dig deeper.
Last edited by Dave H.; 12-29-2007 at 10:41 PM.
12-29-2007, 01:43 AM
#21
What's interesting is that John had the car running and moving..and then he put the air cleaner on there and it wouldn't start. Glad you found it. We had similar issues on JT's turbo motor build. His injector harness was really bad. I think he had to nearly rebuild the whole thing.
I have one bad connector on my GT (pulled wires out of the clip when removing from injector). Had issues with sputtering at over 4k rpm a while back...reseated that wire and it ran fine. I didn't think that one bad injector would kill all of them? Is this the case?
Anyway..good deal...will be keeping my eyes peeled for a blue GTS ripping up the streets around Seattle soon.
Later,
Tom
I have one bad connector on my GT (pulled wires out of the clip when removing from injector). Had issues with sputtering at over 4k rpm a while back...reseated that wire and it ran fine. I didn't think that one bad injector would kill all of them? Is this the case?
Anyway..good deal...will be keeping my eyes peeled for a blue GTS ripping up the streets around Seattle soon.
Later,
Tom
12-29-2007, 04:12 AM
#23
Under the Lift
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The wiring diagrams exposes this. Point 2 is the batch fire signal from the LH feeding all 8 injectors. This is an 89 diagram, so it shows the split power source through points 1 and 4, for the other side of the lead wires, routed from ignition monitoring relay (allowing it to stop half the injectors if needed). Earlier LH had a single power source. Regardless, by the LH taking the power feed through point 2 to ground, you get a batch fire and an easy explanation of why a short in any lead takes all the injectors out.
Last edited by Bill Ball; 12-29-2007 at 03:49 PM.
thank you, we are in business 
12-29-2007, 07:06 AM
#25
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Wow, great thread.
Heinrich, can you change the title to 'The official fuel injector troubleshooting thread'?
.
Glad you're up and running!
Heinrich, can you change the title to 'The official fuel injector troubleshooting thread'?
.Glad you're up and running!
12-29-2007, 11:30 AM
#27
Racer
Malcolm,
the 1988 model doesn't have one.... it came on the 1989 model... so don't worry.
The 1987/1988 model had the 12 volts wired directly to the injectors via two junction points.
The IgnMonRelay is mounted on the LH/EZK mounting bracket, just below the EZK.
the 1988 model doesn't have one.... it came on the 1989 model... so don't worry.
The 1987/1988 model had the 12 volts wired directly to the injectors via two junction points.
The IgnMonRelay is mounted on the LH/EZK mounting bracket, just below the EZK.
12-29-2007, 01:18 PM
#30
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It can't be an official FI thread without a link to Tony's injector journey-
https://rennlist.com/forums/showthre...ight=injectors
My recent injector fiasco-
I had a problem like Tony's after rebuilding my intake. At the same time as my intake rebuild I replaced the in tank and outer fuel pump and the fuel filter, also had the injectors rebuilt. My car wouldn't start... I was suspecting a shorted injector like what Bill Ball had experinced. Porken came over to help diagnose and right away we found none, as in 0, of the injectors were firing when we applied 12v directly to the injecotrs. Repeated quick taps of power freed up 5 injectors but 3 were very stubborn and we had to tap on them repeatedly and repeatedly apply quick 12 v charges before they freed up. I didn't think the rebuilt injectors would be stuck like Tony's, he had bought injectors that had been run for a short period and then not used for a year. Mine were rebuilt about 6-8 weeks ago.
Hope this helps someone.
https://rennlist.com/forums/showthre...ight=injectors
My recent injector fiasco-
I had a problem like Tony's after rebuilding my intake. At the same time as my intake rebuild I replaced the in tank and outer fuel pump and the fuel filter, also had the injectors rebuilt. My car wouldn't start... I was suspecting a shorted injector like what Bill Ball had experinced. Porken came over to help diagnose and right away we found none, as in 0, of the injectors were firing when we applied 12v directly to the injecotrs. Repeated quick taps of power freed up 5 injectors but 3 were very stubborn and we had to tap on them repeatedly and repeatedly apply quick 12 v charges before they freed up. I didn't think the rebuilt injectors would be stuck like Tony's, he had bought injectors that had been run for a short period and then not used for a year. Mine were rebuilt about 6-8 weeks ago.
Hope this helps someone.