Stumped - No Start stock '87 duke

[Cheeze]

I'll preface this post by admitting I've worked on cars and Fieros for about 15 years now and I'm state certified mechanic and automotive engineer (which basically means I'm not a total jackass and the gas tank is not empty).

So the daily driver had been surging a little at idle and one time actually quit idling after 30 seconds. It started to take more and more throttle to launch when cold and I figured it was about time to do the fuel pump. Later that week I drive to work no problems, park, it rained, no start when I went to go home. I saw the tach was still jumping during crank and figured the pump finally went or the rubber tube popped off inside the tank. I jumped the relay just to make sure and it was getting 12V. It cranked, backfired, sputtered, nothing. So I hit up Rock for a new fuel pump, fuel filter, plug wires since they were on clearance and a bunch of little crap. Installed only the new pump and fuel filter and nothing, wtf. Just cranks, not a hint of firing. The throttle blade is freshly wet and there is a puddle of fuel in the bottom of the intake. Both coils produce a strong spark. I can hear the pump run. Check engine light does come on with ignition which should indicate working ECM. Service manual says I need to check fuel pressure so I guess I'll start there tonight. Anyone heard of something like this or have ideas? Went from running to nothing after turning it off and letting it sit for 9 hours in a parking lot.

- Stock '87 Iron Duke base coupe (except suspension)
- Engine rebuilt 4 months ago with new camshaft gears and AC Delco spark plugs
- New Bosch fuel pump and filter screen
- New AC Delco fuel filter
- Newer crank sensor / ignition module / coils (2 years ago)
- Good battery

[Series8217]

'87/'88 Duke ECUs have a conformal coating on them which hardens and shrinks over time, eventually breaking components off the circuit board. This leads to completely random intermittent failure modes that can be impossible to diagnose without just swapping out the ECU for one that is known to be good (preferably remanufactured -- apparently they can strip the coating, reflow the board and recoat it).

On my '88 Duke, the failure mode was the fuel injector was open 100% of the time and no start. The car just stopped while I was driving it. When my assistant turned the key to run, the fuel pump primed a bunch of fuel dumped into the throttle body since the injector was open. No start. If I distorted the circuit board assembly by pushing on it with my hand sometimes it would start and run.

[Cheeze]

Sweet, thanks Series. That helps confirm my diagnosis then. I've owned a fair amount of shitty vehicles over the years and have never replaced an ECM so I was pretty skeptical. I followed the factory service manual diagnostics:

Check engine light on --> good ALDL connection through OBD1 scanner --> TP voltage below 2.5 volts --> correct rpm is read during cranking --> test light fires for two seconds at fuel pump test port on ALDL after ignition on --> injector fires during cranking (WAY too much fuel) --> disconnect injector and no fuel (here is where is got strange for a bit. the car fired up and started running - poorly but went to about 2000 rpm for 3 seconds and quit. I'm guessing burning off all the fuel that was puddled in the intake but strange that it ran. Made me think it wasn't the ECM. I ignored this and continued the diagnostic) --> Connected test light to fuel injector harness --> light did not blink --> Light was constant on --> No ground short found in blue injector wire (circuit 467) --> BAD ECM grounding circuit.

So my next question, where to obtain one? I'm guessing a junkyard is the best place to go to make sure I second guess the ECM for the rest of its life. Are there good and bad remanufactured brands just like all the other parts? I'll assume this is a generic GM parts bin piece like everything else on the car and I just plug in my PROM?

[Series8217]

I bought a reman ECM from the local auto parts store and it worked fine. I may still have it somewhere, but I wouldn't know where to look. Might have been tossed out when I moved...

There's really only one right way to repair the PCB so any reman is probably OK.

[Cheeze]

Ever felt like you have literally been shit on? Got to work this morning and realized my laptop was at home, spilled coffee on my desk, drove all over to look at four houses for sale and they ALL had bad water damage so it's befitting that the new ECM did NOT fix my car.

I bought a A1 Cardone reman from O'rielly with a one year warranty for $83. What are the odds the replacement is bad? Can you have a bad PROM? I have not the time to fix this until after finals next week but I'm not really sure wtf to do. Bad regulator pushing a LOT of fuel or an injector that stays 100% open but only when commanded to open? It does not flow when the pump is priming, only cranking then makes about 5 revolutions and hydro-locks. Disconnect the injector and it will burn the gas in the intake again.

I really don't care that my Fiero is broken again - it's a Fiero. I'm mad that I don't know what to fix.

[Emc209i]

Complete lazy stab in the dark on my part, but is the fuel pressure regulator leaking fuel? A new pump or stronger pump could rupture an old diaphragm and feed raw fuel to the intake. Easy to rule out by removing the air filter to look.

[Series8217]

Ever felt like you have literally been shit on? Got to work this morning and realized my laptop was at home, spilled coffee on my desk, drove all over to look at four houses for sale and they ALL had bad water damage so it's befitting that the new ECM did NOT fix my car.

I bought a A1 Cardone reman from O'rielly with a one year warranty for $83. What are the odds the replacement is bad? Can you have a bad PROM? I have not the time to fix this until after finals next week but I'm not really sure wtf to do. Bad regulator pushing a LOT of fuel or an injector that stays 100% open but only when commanded to open? It does not flow when the pump is priming, only cranking then makes about 5 revolutions and hydro-locks. Disconnect the injector and it will burn the gas in the intake again.

I really don't care that my Fiero is broken again - it's a Fiero. I'm mad that I don't know what to fix.

Well that's a bummer! I'm out of ideas besides the replacement ECU being bad. Unlikely, but possible. A bad PROM should be detected by the checksum routine, so I don't think that's it.

[jelly2m81]

The other thing I have come across with those dukes that exhibited a similar condition is the fuel pressure regulator and metering cover / injector O-rings failed. What happened was while cranking it was dumping fuel.

I would check 2 things. First remove the fuel injector connector. Have a helper crank the engine while you watch in the throttle body for any fuel release. There should be nothing.
With the injector reconnected there should only be an even conical spray pattern, and pooling or dribbling indicates a failed seal under the metering cover.

The 2nd thing is your no start. Pull the plugs and see if they are wet, when they get saturated with fuel the plugs will not fire. and excessive fuel going into the combustion chambers is only compounding the no start.

Another though, pull the dipstick, does the oil smell like gas?

RockAuto has the throttle body rebuild kit for less than 30 bucks if that turns out to be your issue.

[The Dark Side of Will]

I bought a A1 Cardone reman from O'rielly with a one year warranty for $83. What are the odds the replacement is bad? Can you have a bad PROM?

Does it *HAVE* a PROM?

[Cheeze]

F-me. The saga continues.

Does it *HAVE* a PROM?

Are you asking if there are ones and zeros on the prom chip? I'll have to answer with "I don't know."
Or are you asking if I'm too stupid to read the big blue sticker on the new ECM that reminds me to put the prom in from the old ECM? I was hoping to avoid that kind of 'help' by staying off Old Europe.



So get this. I picked up the fuel pressure test gauge and put it inline in the correct fuel supply line. 10 pounds with key on and moves to 12 pounds while cranking. Pressure is within spec. Hook up the injector and it floods instantly. A huge conical flow just pours out the injector and ONLY the injector. Fuel is not coming from any other location. So I figure why not install part of the throttle body rebuild kit since I have it now? New injector screens, new injector o-rings. Reinstall injector, it runs! I get out to look at the fuel flow pattern and to my surprise there is a huge fountain of fuel spraying upward from the injector. I pee my pants a little and quickly turn the car off. I pinched the upper o-ring during installation and cut it. I use a little oil as lube and reinstall another o-ring that was in the kit. No leaks this time but the car instantly floods out again.

Ugh. I have another '87 Fiero duke motor so I pull that injector and stick it in. Still good fuel pressure only this time nothing comes out at all. The spare motor sat in some dudes shed for 5 years and got rained on for a couple months before I bought it from him. I blow out the original injector from the pintle side with screens off and reinstall. Instant flood.

Two bad fuel injectors? I HATE HATE HATE troubleshooting by replacing parts like a know-nothing shadetree idiot but I'm really running out of idea - again.

So, Rock Auto:

STANDARD MOTOR PRODUCTS Part # TJ14T
Throttle Body Injector; w/ O-ring One of our most popular parts
$55.79 $0.00 $55.79

ACDELCO Part # 19304544
Professional (Only 1 Remaining)
$110.89 $0.00 $110.89

AIRTEX / WELLS Part # 4G1775
17111986
$177.79 $0.00 $177.79


AUTOLINE Part # 15918
Reman
Injector
$27.79 $30.00 $57.79

GB REMANUFACTURING Part # 83115101
Remanufactured T/B Injector
$25.89 $35.00 $60.89

Are these other guys junk? I've only heard of AC Delco. Pretty silly I've just put almost $300 into a $600 car for this no-start issue now. Need to get this thing running soon so I can remind myself why I still drive it. F-150 and company cars have been feeling pretty good to drive around.

[ericjon262]

Check the tps, I had an old camaro do the same thing, new tps and everything cleared right up.

[ericjon262]

Also don't jump to conclusions, you didn't say you replaced the prom nor did we see the PCM , the statement will made wasn't to say you're dumbass. Most of us here also acknowledge that mistakes happen, and people forget things.

[Cheeze]

Thanks for the suggestion Eric. I checked TPS with the scan tool. It's reading 0.75 volts at closed pedal and will move upward linearly with throttle opening. I believe if TPS is over 2.5 volts the engine will not start as it recognizes this as a frozen open throttle condition. But they are cheap enough to replace anyways. I'm actually surprised it was still giving good readings. One time the injector filled the throttle body with fuel so fast that it was leaking out the sensor.

[Emc209i]

Ever replace the fuel pressure regulator?

Good on you trying to find the specific cause, I'd have found a running duke by now and swapped the entire throttle body assembly to see if the problem went away.

[Cheeze]

Ever replace the fuel pressure regulator?

I did not replace the regulator yet since the pressure was within spec but I guess it's worth a try as well. And I've been looking for a running duke and turns out that is just as hard to find as making one run. These used to be a dime a dozen when I was growing up but it appears all the cars that had them were worth more as scrap.



And I apologize for snapping earlier. It was pretty harsh of me but I was fuming with frustration at the time I posted. This seems like a simple problem on a simple engine.

[Emc209i]

One of the most frustrating cars I've ever worked on was a TBI 350. Seems like a simple concept, but all the carb technology mixed with fuel injection made for some migraine inducing problems. Vent away man, we all understand.

The F-body guys have flooding when their regulators go out because the regulator lowers the pressure during start and idle. I have no idea if the duke TBI works the same way but the units look identical minus an injector. But I just looked up the stock idle pressure and it says 9-13 lbs. I have no idea.

[Cheeze]

My car is officially a woman. I didn't understand any of the logic behind low fuel pressure causing a flood rich condition but I'm desperate. I read the S-10 forums for a while then just head out to change the fuel pressure regulator diaphragm. Got it in there the right way, tightened it down, key on, no leaks. Sweet. Also no fuel pressure now on the gauge. *Insert curse words* Whatever, I'll crank it anyways - floods out exactly the same as before. Huge puddle in the intake, about a quarter inch on the throttle blade in MAYBE 3-4 revolutions. S-10 guy got his truck to fire holding the pedal at WOT. I've heard about the "clear flood mode" but if it's always flooding what's the point? I expected a high revving engine and it starts, revs high (for a duke maybe 3500 rpm) and I'm pissed so I just keep it there. "Fuck you iron duke, I hope you blow up with this high idle cold start." I quickly jump out to watch it flood itself to death and choke and that not what happened. This is:

https://youtu.be/Hmf-JmvKIk4

It calms down to a normal idle albeit with a now noticeable tick from the throttle body area. I wait and wait and it doesn't die. The inline pressure gauge still reads 0 psi. Now does that make ANY F-ing sense to anyone? Seriously. This is a true story. I left it at work to do an oil change and coolant flush tomorrow but I'm kind of not believing what just happened.

[The Dark Side of Will]

mistakes happen, and people forget things.

And not all reman ECM's come with a big blue sticker.

Have you tried a *different* PROM? Seems like that's the only thing in the system you haven't changed.

Hot wire the pump... if the injector holds pressure while the ECM is off and floods the engine once you turn the ECM on, the problem's not the injector.

[The Dark Side of Will]

It calms down to a normal idle albeit with a now noticeable tick from the throttle body area. I wait and wait and it doesn't die. The inline pressure gauge still reads 0 psi. Now does that make ANY F-ing sense to anyone? Seriously. This is a true story. I left it at work to do an oil change and coolant flush tomorrow but I'm kind of not believing what just happened.

I'm not familiar enough with the TBI system to know what would cause 0 gauge pressure other than a blocked gauge port.

My BMW had a SOLID blockage in the return line inside the tank... it would run, but had about 80 psi of fuel pressure against a dead-headed regulator.

[Cheeze]

I'm still at war with my car but I'm going to keep this post going with what I've done and what helped so maybe someone down the road can read it and my suffering won't be completely in vain.

The car now starts but ONLY if I WOT during cranking to activate "clear food mode." Today the car does not idle correctly but stays at 2000 rpm. The oil is not diluted yet with gasoline but I will be changing it as soon as the engine is fixed. I swapped back to the original ECM to see if it changed anything, it did not. At first I heard the fan come on with 'key on' position and the car started and ran the same (WOT start, high idle). I quickly realized the fan was on because I did forget to swap back the PROM and it came on as default. Car running the same made sense though seeing as it was open loop cold start. But now the IAC pintle stays fully retracted and will not compensate out over time. Maybe the flooding backfires pushed it in and broke it? Maybe backfires popped the throttle body gaskets or mushy rubber lines connected to it?

I think I have a multitude of problems. First I took the fuel pressure gauge hose off the dial and noticed a piece of rubber from the schrader valve seal was in there. It is a rental tool and the rubber was wearing down from use. I cleaned it out but who knows if I got it all. I'm taking it back to get a different one at another store.

But I was also doing a lot more reading and thinking about your guys' posts. I think this is LOW fuel pressure from a clog causing a flood condition. New pump could have dislodged something although I did change fuel filter at the same time. Nothing much else makes sense. The MAP and coolant temp should be ignored until closed loop and my scanner says air temp is pretty accurate ('87 first year for IAT). EMC, you were right, lots of TBI 350 guys with similar symptoms (though hardly anybody follows up to say what fixed the problem). http://forums.superchevy.com/chevy-high ... ecu-codes/

Here is a site dedicated to listing the issues for flooding but it doesn't really guide you in a troubleshooting sort of way.
http://www.fixkick.com/flooding.html

I think this is the best document I have found so far and gives step by step how to troubleshoot TBI systems (PDF download)
http://www.google.com/url?sa=t&rct=j&q= ... jSssXrZVNA

So today's plan is verify correct fuel pressure. New gauge. I did key on with the supply line disconnected from the TB and it pushed out a good amount of fuel when it primed but I didn't measure the volume to compare to the factory spec. So I'm hoping the block is in the throttle body because I already have the rebuild kit and I don't want to drop the tank again to disconnect the fuel pump and blow out the supply and return line.