S5 Turbo Fuel Issues

Pete_89T2 · 09-04-2016, 07:57 AM

Hmm, not sure. I'm assuming the car is cranking strong, just not starting, and you checked for any stored CEL codes.

My best guess at this point is it's a wiring harness issue - something is preventing the either the fuel pump from running OR the FIs from firing. Time to crack out the FSM schematic diagrams & go to war.

Couple of ideas to try to troubleshoot further:

1. Try jumping the yellow 2 pin fuel pump test connector. It's located on the passenger side strut tower off of the main ECU harness. With the key in the "run" position, you should hear the pump running constantly when it's jumped.

2. Also with the key in run, check voltages between each FI's "A" terminal pin (per FSM schematic) and ground. All should be reading +12V. If you're not seeing +12V, none of the injectors will fire. If you look at the FSM schematics, you'll see that all of the FI's share a common +12VDC, supplied thru the main relay.

JL1RX7 · 09-04-2016, 08:17 AM

Yep did all of that. Battery fully charged, etc. When you use the jumper on the yellow connector it purrs like a kitten. When checking the voltages across all the relays they all read like they should. All OHM readings check good per FSM. Used my other FC's for spare relays, etc to swap in. Still nothing. Which is why I am stumped as hell.

Pete_89T2 · 09-04-2016, 10:09 AM

So when you jump the yellow check connector the FP runs as it should. Have you tried starting & running the car with the check connector jumped? If so, what happens?

And just to be clear, you checked the voltages between each FI connector terminal & ground, and are reading +12V on the "A" terminal, and 0V on the "B" terminal of each FI?

JL1RX7 · 09-04-2016, 11:28 AM

Even tried that. It still wouldn't start more than a second. It seems that it's not switching from start to run. Just changed plugs for shits and giggles. Still doing the same thing.

Yes on the switching relay under the steering wheel it has voltages where it should according to the FSM.

About to change the fuel filter today, again to eliminate any thing else.

Pete_89T2 · 09-04-2016, 12:12 PM

Quote:

Originally Posted by JL1RX7

Even tried that. It still wouldn't start more than a second. It seems that it's not switching from start to run. Just changed plugs for shits and giggles. Still doing the same thing.

Yes on the switching relay under the steering wheel it has voltages where it should according to the FSM.

About to change the fuel filter today, again to eliminate any thing else.

^That's not where I said to measure it - you need to measure AT each FI connector to rule out a FUBAR'ed ECU harness wiring to the injectors. Which sucks because you have to pull the UIM to get in there, but that should be pretty easy for you by now.

A harness failure on a 25+ year old T2 isn't uncommon, and I have a hunch that the common +12V source to the injectors may be open somewhere - that would show up as a sudden no start/no run symptom. With the key in "run", you should be seeing +12V at the "A" terminal of all 4 injectors, and 0 at all the "B" terminals. Just use a paper clip to back-probe the connectors with your DVM, measure between each terminal and ground.

vrracing · 09-04-2016, 12:18 PM

It's really hard to tell from the posts what is actually happening.

"When you use the jumper on the yellow connector it purrs like a kitten."

suggests that it runs fine if the jumper is connected.

But then right after that...

"Pete_89T2 -So when you jump the yellow check connector the FP runs as it should."

to which you respond...

"Even tried that. It still wouldn't start more than a second."

If it "purrs like a kitten" with the yellow jumped but dies if you pull out the jumper, I'd look at the AFM. IIRC, there is a safety feature that if the AFM isn't telling the ECU there is air flowing (that is, the engine is running) then the ECU cuts the fuel pump. That way, if you wreck with the key on, the fuel pump doesnt feed gas to the impending explosion. That is disabled when the key is in "start" as opposed to run because obviously the engine isnt turning over enough to activate the AFM.

Hope that helps.

JL1RX7 · 09-04-2016, 12:26 PM

Sorry should have made that more clear, when you put the jumper in the yellow connector, the fuel pump runs like it should. Now even leaving that jumper in there the car starts for a second then dies.

I agree with you on the AFM. But putting a known good one should have made that go away. But it didn't. I don't have a spare turbo ECU to swap that out to cross that off the list.

Pete haven't pulled those yet. Trying everything else before I did that. Going to the store to buy new hose clamps before I dive down that rabbit hole.

vrracing · 09-04-2016, 01:00 PM

Have you put a fuel pressure gauge on the system?

09-04-2016, 12:18 PM	#6
vrracing Rotating Assembly Join Date: Oct 2008 Location: TX Posts: 102 Rep Power: 17	It's really hard to tell from the posts what is actually happening. "When you use the jumper on the yellow connector it purrs like a kitten." suggests that it runs fine if the jumper is connected. But then right after that... "Pete_89T2 -So when you jump the yellow check connector the FP runs as it should." to which you respond... "Even tried that. It still wouldn't start more than a second." If it "purrs like a kitten" with the yellow jumped but dies if you pull out the jumper, I'd look at the AFM. IIRC, there is a safety feature that if the AFM isn't telling the ECU there is air flowing (that is, the engine is running) then the ECU cuts the fuel pump. That way, if you wreck with the key on, the fuel pump doesnt feed gas to the impending explosion. That is disabled when the key is in "start" as opposed to run because obviously the engine isnt turning over enough to activate the AFM. Hope that helps. __________________ 90 S5 Vert. JDM Tii with BNR Stage1 turbo. Pineapple Racing street port. Bonez cat-forward. Corksport cat-back with Vibrant UltraQuiet resonator. RTek 2 wZeitronix w/b. HKS EBC. Vis CF Tii hood. 3000GT wing. Ground Control coilover kit with KYB AGX shocks. Red and Black leather RX8 seats. Corksport Odura lip & bumper caps, OEM Tii skirts Last edited by vrracing; 09-04-2016 at 12:41 PM.

09-04-2016, 12:26 PM	#7
JL1RX7 Rotary Fanatic Join Date: Feb 2008 Location: Front Royal, VA Posts: 487 Rep Power: 18	Sorry should have made that more clear, when you put the jumper in the yellow connector, the fuel pump runs like it should. Now even leaving that jumper in there the car starts for a second then dies. I agree with you on the AFM. But putting a known good one should have made that go away. But it didn't. I don't have a spare turbo ECU to swap that out to cross that off the list. Pete haven't pulled those yet. Trying everything else before I did that. Going to the store to buy new hose clamps before I dive down that rabbit hole. Last edited by JL1RX7; 09-04-2016 at 12:31 PM.

09-04-2016, 01:00 PM	#8
vrracing Rotating Assembly Join Date: Oct 2008 Location: TX Posts: 102 Rep Power: 17	Have you put a fuel pressure gauge on the system? __________________ 90 S5 Vert. JDM Tii with BNR Stage1 turbo. Pineapple Racing street port. Bonez cat-forward. Corksport cat-back with Vibrant UltraQuiet resonator. RTek 2 wZeitronix w/b. HKS EBC. Vis CF Tii hood. 3000GT wing. Ground Control coilover kit with KYB AGX shocks. Red and Black leather RX8 seats. Corksport Odura lip & bumper caps, OEM Tii skirts

09-04-2016, 07:57 AM	#1
Pete_89T2 Lifetime Rotorhead Join Date: Apr 2010 Location: Elkton, MD Posts: 874 Rep Power: 16	Hmm, not sure. I'm assuming the car is cranking strong, just not starting, and you checked for any stored CEL codes. My best guess at this point is it's a wiring harness issue - something is preventing the either the fuel pump from running OR the FIs from firing. Time to crack out the FSM schematic diagrams & go to war. Couple of ideas to try to troubleshoot further: 1. Try jumping the yellow 2 pin fuel pump test connector. It's located on the passenger side strut tower off of the main ECU harness. With the key in the "run" position, you should hear the pump running constantly when it's jumped. 2. Also with the key in run, check voltages between each FI's "A" terminal pin (per FSM schematic) and ground. All should be reading +12V. If you're not seeing +12V, none of the injectors will fire. If you look at the FSM schematics, you'll see that all of the FI's share a common +12VDC, supplied thru the main relay.

09-04-2016, 08:17 AM	#2
JL1RX7 Rotary Fanatic Join Date: Feb 2008 Location: Front Royal, VA Posts: 487 Rep Power: 18	Yep did all of that. Battery fully charged, etc. When you use the jumper on the yellow connector it purrs like a kitten. When checking the voltages across all the relays they all read like they should. All OHM readings check good per FSM. Used my other FC's for spare relays, etc to swap in. Still nothing. Which is why I am stumped as hell.

09-04-2016, 10:09 AM	#3
Pete_89T2 Lifetime Rotorhead Join Date: Apr 2010 Location: Elkton, MD Posts: 874 Rep Power: 16	So when you jump the yellow check connector the FP runs as it should. Have you tried starting & running the car with the check connector jumped? If so, what happens? And just to be clear, you checked the voltages between each FI connector terminal & ground, and are reading +12V on the "A" terminal, and 0V on the "B" terminal of each FI?

09-04-2016, 11:28 AM	#4
JL1RX7 Rotary Fanatic Join Date: Feb 2008 Location: Front Royal, VA Posts: 487 Rep Power: 18	Even tried that. It still wouldn't start more than a second. It seems that it's not switching from start to run. Just changed plugs for shits and giggles. Still doing the same thing. Yes on the switching relay under the steering wheel it has voltages where it should according to the FSM. About to change the fuel filter today, again to eliminate any thing else.