First Run, Issues

[vreference]

After an aborted attempt yesterday that involved fuel spraying out of the fuel lines I did not replace, I ran the engine for the first time since it was removed from the car last fall. It started and idled very reassuringly for about 15 seconds and then the idle became rough and it died. I was unable to restart it or even get it to hit on one cylinder after many attempts. I reseated the crank position sensor connectors and then resorted to a bit of starting fluid. Starting fluid seems to confirm I have spark as it does fire intermittently but no semblance of an idle. I even flipped the reference and speed sensors just to be sure (although I doubt it would have idled so well had they been wrong) and again it sputtered on starting fluid (does it make sense that it would do that with the sensors plugged in wrong?)

I cracked open the fuel rail and fuel came out, also I had plenty of flow yesterday so I don't have much reason to suspect supply.

Does this behavior sound familiar to anyone? I don't smell raw fuel coming out of the exhaust so I suspect I have some idea where to start but I'm about stumped. If nothing else, is there a place in the engine compartment I can jumper to run the starter remotely?

In return I give you a few pics of what has happened.

[Zeke]

My first thought would be a fuel issue as in old contaminated gas left in the car.

[vreference]

Well, I thought it might be possible but the fuel smells and looks very good. I put a hose on the test port and cranked for a few seconds (I assume it's normal for the motronic cars not to pump or even prime until the engine is rotating?) and did get what appears to be an appropriate amount of fuel out (although I did not actually preform the volume test.)

You still leaving at 20K posts?

[vreference]

Can anyone confirm that my tach should or should not move while cranking?

[kidrock]

my tach does not move while cranking.

[vreference]

Well, I have spark so I guess I need to find a way to diagnose fuel beyond checking supply. Seems really unlikely that all six injectors had some sort of mechanical failure at once. I'm certainly glad it ran so well for a few seconds or I'd be really nervous.

[vreference]

Timing light seems to confirm what I was seeing at the plug this morning. Intermittent spark. When it does spark it's weak. Good power to the coil. Otherwise the timing appears to be retarded by quite a bit, it took me a while to find the mark, I didn't expect to see it so far to the right, retarded by 10-15 degrees or more? Really wishing I had a scope now.

The weak spark is harder for me to explain but I think the lack of fuel coming out of the exhaust seems to indicate the issue is well upstream of the coil and is effecting both fuel and ignition.

[vreference]

At the ECM harness I confirmed,
12v at 18 & 35
Fuel pump runs with ground to 20.
Air Temp: Resistance between 6 & 22
Crank Speed Sensor: Approx 1K Ohm
Reference Sensor: Approx 1K Ohm
Both groups of Injectors Click when Grounded (14 & 15)
Very low impedance at Coil.

I still don't have any ideas, still seems Like I need to get a hold of a scope.

[Formerly Steve Wilkinson]

Am I missing something, or did you respond to Milt's suggestion that it might be bad gas by saying you had analyzed the fuel by nose and eyeball and determined that it was good?

[JerryL]

Current day fuel sucks, the stabalizers are gone, a month or two is bad start using the stalalizers if storing a month +.
If you have been since Nov or so dump it and get some fresh premimum and give it a shot.

Regards

[vreference]

Ha, well with all the vehicles and small engines I've had and maintained I feel like I know what I'm looking for concerning gasoline. Also it ran very well on the same gas briefly and now I have a very intermittent spark (often no fire for 3 or 4 compression strokes) and not even the faintest hint of unburnt fuel coming out of the exhaust.

I'll get it I suppose.

[Wayne 962]

It started, ran fine for 15 seconds and ran rough and died? That does not sound like an electrical problem to me, sounds like a fuel delivery or clog problem somewhere. That is where I would concentrate my efforts.

-Wayne

[rfloz]

The fuel may be "okay", but you might have dislodged some crud during disassembly/assembly.

Did you check the injectors for flow? Did you check the spark plugs for signs of fouling or lean burning?

[vreference]

The trouble with the fuel clog idea is that it has to be the injectors as everything checks out at the test port including check valve. So, all of them had to become clogged at more or less the same time. Which is certainly not impossible but I'm having a hard time ignoring what probably ammounts to spark only 2/3s of the time. If even one were flowing I would expect to get a pretty solid hit on one cylinder (not counting the ignition issue anyway) I wouldn't be shocked to find the remains of an exploded fuel filter everywhere but what came out of the test port is perfectly clean. I'm always up for a good automotive mystery.

[vreference]

As the car is here and the scope I have to drive to pickup I pulled a fuel rail. I put injectors in the vice and with some fuel, compressed air, and 12v tested the left bank without disturbing any sediment that might be at the top. All three appear to have a good pattern.

Also, passed the fuel pump flow test easily with well over 1 quart in less than 30 seconds. Mowed the lawn on the fuel from the test without incident.

[vreference]

Finally getting around to working on this again; still waiting on the scope (but as my last post was over a month ago you can see how motivated I am). I searched some other no-start threads and found one for an '87 where people suggested using an LED test light across the coil primary and across an Injector lead. to test for ignition and fuel respectively.

I'll start by saying, I may have narrowed it down to one of my crank sensors but without knowing the inner workings of the DME - I can't say. I switched the sensor positions and now have consistent spark. I checked it many times before switching the sensors and appeared to have very intermittent spark. Now the reference sensor is where the speed sensor was and vice versa; the plugs were switched as well. I had assumed that maybe the speed sensor was only for the tach and the DME took all of the information it needed from the reference sensor. With an LED test light I confirmed a good signal to the ignition coil but get nothing (but continuity) from the injector harness.

I suppose this all adds up if anyone can confirm that the speed sensor is required for the car to run.

Also, I never read about an alignment procedure for the bracket these sensors are in. I know there is a specification for how close they should be to the tone ring. Does everyone just bolt them on and not worry about it? How sensitive are they to the gap? I never once read anything about any issues related to mounting them.

[DW SD]

Do you smell fuel from the exhaust after cranking for 15 seconds?

Can you be certain the fuel pump is running when cranking? I'd put a test light on the pump under cranking. This would confirm that the DME is in fact turning on the pump. If it turns on the pump, you know the crank position sensor is working as the DME will not turn on the pump without "seeing" movement of the crank.

Buy a $5 noid light to make sure the injectors are getting triggered from the DME. The injectors are pulsed, so not sure the voltage would register on a volt meter.

Can you test the fuel pressure at the rail?

I wouldn't be surprised if debris jammed up your fuel pump, which only has a screen in the tank to remove debris. My fuel pump clogged with bits from a new fuel cell. Shot in the dark, but this is where I'd focus.

Doug

[vreference]

Originally Posted by DW SD

Do you smell fuel from the exhaust after cranking for 15 seconds?

Can you be certain the fuel pump is running when cranking? I'd put a test light on the pump under cranking. This would confirm that the DME is in fact turning on the pump. If it turns on the pump, you know the crank position sensor is working as the DME will not turn on the pump without "seeing" movement of the crank.

Buy a $5 noid light to make sure the injectors are getting triggered from the DME. The injectors are pulsed, so not sure the voltage would register on a volt meter.

Can you test the fuel pressure at the rail?

I wouldn't be surprised if debris jammed up your fuel pump, which only has a screen in the tank to remove debris. My fuel pump clogged with bits from a new fuel cell. Shot in the dark, but this is where I'd focus.

Doug

Thanks for the reply, most of this has been addressed in the unending stream of my posts.

I went through all the DME tests listed in the bently manual and confirmed that the fuel pump does run and the flow rate at the test port is in excess of the specified volume/time. And I did also confirm that it pumps fuel while cranking. Also, I've always gotten at least intermittent spark so the DME is being informed then engine was rotating, if intermittently.

I do have an LED test light and others have confirmed that these will work to confirm signal to the injectors. I see no signal durring cranking at this time.

I don't have a way to check fuel pressure but I know it is building considerable pressure and the check valve is also in working order; that with the passed fuel volume test plus the lack of signal to the injectors leads me to believe I need to look elsewhere.

And no - there has never been even a hint of unburned fuel out of the exhaust which would not be a function of the fuel; it still smells very unburned I can assure you.

[kidrock]

sounds like the speed and/or reference sensors.

[DW SD]

VFR-
OK. I think the injectors are batch fired. Can you confirm good ground to the injectors? If, so, I would focus on the DME and whether the injector driver circuits may be burned out.
Can you swap DMEs with a friend or other Pelican?

Doug