2G 2G Cranks but wont start

[91dsm]

I have a 1995 GSX thats been 6 bolt swapped. The car ran perfectly fine until it sat for about a year. I have done almost everything but replace the ECU which I am beginning to suspect as the issue. Here is the troubleshooting I have done so far.

• I have spark
• 43.5 psi of fuel pressure at the rail
• I can see the CAS signal in Link
• 12V at the injectors
• checked fuses and relays
• coolant temp sensor working
• seeing signal from the MAF in Link
• tested injector resistor pack

In spite of this the injector duty cycle is only 2.5% while cranking. Outside of a wiring issue or ECU are there any reasons for this no start condition ? Thanks in advance.

 

[91dsm]

Short log while cranking

 

[Justin DuBois]

compression? How old is the gas?

 

[91dsm]

compression? How old is the gas?

Compression is good and the tank was just drained and refilled with new gas.

 

[chrysler kid]

Something is not adding up if everything you say is correct, how are you verifying fuel pressure?

Assuming compression results of atleast 100psi per cylinder the car needs fuel, air, and spark to run.

is the battery healthy? Have you tried using a jump box?

Does spraying brake cleaner into the intake manifold through the pcv tube make a difference to the car trying to start?

 

[steve]

Please log the battery and Baro. Check the plugs to make sure they are not fuel fouled.

 

[CrazyDave]

I'm helping the OP with this car. Car is not getting an injector pulse from the ECM. Have 12 volts on all injectors pins. Injectors ohm out at/around 3 ohms. Resistor block reads around 6 ohms on each pin.

Found a ground in the passenger floor panel that is rusted and corroded (looks like car had water damage that wasn't drained in time), Also took ECM apart and the board looks to be corroded in some areas more than others.

Physically took MFI relay apart and that looks brand new, forget the pin numbers, but Ohmed them and "seems" to be a working relay.

I don't have a picture at the moment, but does anyone know the ground that's located at the ABS module's function also has a relay attached to it that's toasted as well.

Fuel pressure was measured while cranking at 40 psi with a mechanical gauge.
I also put a new DW pump in it. Can hear fuel pump running when cranking.

I believe the ECM is a 98 with DSMLink chip installed. Also has a 91 CAS installed.

Who rebuilds ECM's, and where could I find factory pigtail connectors?

 

[pauleyman]

If its got ecmlink, post a log

 

[CrazyDave]

Log is posted above with 91DSM.

PCB has some corroded spots on some transistors in the ECM. I'm narrowing this down right now to No Ground/weak ground for the injectors through the ECM.

Apparently, car will run with starting fluid but haven't verified yet. But I had a noid light in the injector connector and didn't light up. Pulled plugs and they are not fouled, nor coated with fuel, cylinders are bone dry. Only thing I can think of to at least make this car sparkle is adding fuel to it.

The ground I'm talking about has 5 wires going into 1 10mm stud in the passenger foot well.

ECM is a 95 with ECMLink to be correct, not a 98.

On a side note, in ECMLink, is the actual pulse width or the commanded pulse width being displayed in current data for injector pulse width?

Sorry for the questions, I'm new to this platform.

Also admin, Feel free to relocate this thread, not a Newbie post IMO.

 

[Justin DuBois]

I had a post in draft, was going to ask a question and missed sending it. The question was - Have you opened the ECU? Lol...

I could be wrong - I assume ECMLink is reporting IDC (injector duty cycle) as a function of the signal it is sending to modulate the ground - pull down on the injector coil. I don't think it has a way to monitor the injector itself.

 

[steve]

The IDC reported is what was computed based on airflow and the various enrichments. The ECU then uses that with position data to schedule the injector firing.

 

[CrazyDave]

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[steve]

That's where someone cleaned the waxy conformal coating to replace the capacitor. The white edge is the residue.

I don't see anything in that photo to be worried about.

 

[CrazyDave]

Sorry it took so long to upload second photo. I almost want to try to clean it, but the transistor seems like its best days are behind him, . I have an ultrasonic cleaner, might just risk it

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[steve]

I have an ultrasonic cleaner, might just risk it

I wouldn't. As mentioned we need a fresh log with at least the items in post #6 included and it would be better to log everything at this point.

 

[chrysler kid]

Sorry it took so long to upload second photo. I almost want to try to clean it, but the transistor seems like its best days are behind him, . I have an ultrasonic cleaner, might just risk it

Test connectivity or resistance on the board and test resistance between 2 clean points and 2 suspect points.

I wouldn’t clean it in an ultrasonic cleaner but use isopropyl alcohol on a Q tip

 

[steve]

So far I haven't seen anything that is cause to do anything to that ECU besides check connectivity of the traces to R87 and around IC2. If you want to continue down that path, let see the whole board.

The Injector drivers are the black transistors in the upper right in this picture.

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[CrazyDave]

So I replaced some grounds on the passenger floor that were smoked. put the ECM back in this morning and still no start, using a small LED across the injectors I had a very small pulse, Replaced that with a 194bulb and it did not light that bulb.

So I was poking around again and this 60A fusible link fuse is good, but when I pulled the fuse and ohmed both pins to Ground I have about 26ohms on one side and A ridiculous about on the other side, The 20A fuse also has continuity on both pins in the fuse box.

This car also has this anti-theft plug as well.

I did clean the ECM with alcohol but didn't apply any conformal coating (planned on sending it in to ECUlink and didn't want to muck the board up too much) actually looks really good after cleaning it with a soft tooth brush and 99% iso.

Can hear and feel the ignition/fuel pump relay clicking


I think I should send the ECM in to at least get a clean bill of health.

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[CrazyDave]

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[CrazyDave]

Good news to report. I do have an Injector pulse now. Verified with a Noid light. So as of now the electrical circuit seems to be in operating condition for the injectors at least. Took my power probe to the injectors themselves and applied 12v to them....they don't click or anything, I think the fuel may have been so bad that it mechanically locked these injectors when it sat.

Can someone recommend good injectors for this car? Currently has a 14b turbo I think?? Looking at 400hp max. Just a street car. If this car ever drives again I will worry about upgrading the turbo

 

[Justin DuBois]

Good news to report. I do have an Injector pulse now. Verified with a Noid light. So as of now the electrical circuit seems to be in operating condition for the injectors at least. Took my power probe to the injectors themselves and applied 12v to them....they don't click or anything, I think the fuel may have been so bad that it mechanically locked these injectors when it sat.

Can someone recommend good injectors for this car? Currently has a 14b turbo I think?? Looking at 400hp max. Just a street car. If this car ever drives again I will worry about upgrading the turbo

Sure - injectors will clog, just sitting. I suggest you have them cleaned and ballanced. Contact: https://www.rcfuelinjection.com.
You can also buy new. Now is a good time to put in a new fuel filter.

A stock 95 gsx came with 450cc denso low resistance (low z) injectors. These were chosen to balance with 8.5:1 compression 2G pistons and a T25 stock turbo at ~7-15psi boost levels.~210hp (190lph fuel pump)

With the right modifications, you can use a wide array of injectors low or high resistance, at whatever size you are building for.

I've run 660cc injectors, a Big 16G turbo at 18lbs boost on 91 pump gas using a MAF and an AFC (260lph fuel pump)
I'm currently running 1000cc injectors with a Bastard 20G at 23-25 lb of boost on E85 with speed density mode using a 95 ECU with ECM Link v3 - making ~400whp (340lph fuel pump)

 

[CrazyDave]

Great news to report tonight, Installed new 1000cc FIC injectors and the car fired up. Ran it for about 2 minutes total and checked around for leaks. Oil light was on when revved then off at idle, Going to put a mechanical gauge on it to see actual pressure

When I took the injectors out there was varnish sitting inside the bungs for the injectors, I imagine that is what lead to the injectors failure. The gas that was originally drained was the worst I've ever seen or smelled.

Not sure I needed to take the ECM apart and clean it, , (Although not sorry I did) but I'm going to coat it in conformal and seal it back up. I'm glad I stumbled upon all those grounds corroded and cleaned them up, defiantly didn't hurt the cause to make this car run again.

Now to move onto the frozen clutch pedal.....

Thank you to all involved, haven't been on a forum in 10+yrs thanks for the help.