88 Iron Duke will not start, but will idle (Page 1/2)
DanMFiero88 AUG 20, 04:55 PM
Hi everyone,

My Iron Duke has recently developed a problem where it will not start, but will idle once I can get it started.

When I turn the key to the Start position, a small spray of fuel comes out, but the engine will not start. When I return the key to the "On" position, some fuel drops into the bowl. If I do this 2-3 times, there is enough fuel in the bowl to briefly start, then it dies.

If I remove the injector, about a teaspoon of fuel drops into the bowl.

If I attempt to start again after replacing the injector and putting everything else back together, the engine will start after 1-3 attempts. Due to being flooded, the engine has rough idle for between 30-45 seconds and then settles in to an idle between 800-1100 rpm. Average is around 900 rpm.

When idling, the spray pattern from the injector is what you would expect - consistent spray in a fan pattern. I can rev the engine and it will return to idle without dying.

Thus far, I have:
- Replaced the fuel injector
- Replaced the fuel filter
- Replaced the fuel pressure regulator diaphragm
- Replaced the PCV valve (I realize that this should not have anything to do with the problem, but the old one, while functional, was nasty)

Any ideas about what is going on here?

Thank you in advance.
Patrick AUG 20, 05:01 PM
When you turn your key to ON (not START), do you hear the fuel pump prime for two seconds? And does fuel not exit the injector at this point? (It shouldn't.)

[This message has been edited by Patrick (edited 08-20-2022).]

DanMFiero88 AUG 20, 05:31 PM
Thank you for responding! Yes, I hear the fuel pump, and no, no fuel comes out of the injector until I move the key from On to Start.
Patrick AUG 20, 05:38 PM

My first Fiero 25 years ago was an '87 duke. I never liked that engine, and the '88 duke is very similar. Hopefully The Ogre sees this thread and responds. He's quite familiar with these engines.
DanMFiero88 AUG 20, 05:46 PM
Thank you so much, Patrick. It’s weird because this problem just started. I didn’t change anything, so I can’t zero in on a fix.
Patrick AUG 20, 05:57 PM
I suspect something has failed that's supposed to act as a "choke" when you are cold starting your engine. Could be the MAT (Manifold Air Temperature) and/or the CTS (Coolant Temperature Sensor). If either sensor is reading too high, your engine won't be supplied a rich enough mixture to cold start.

[This message has been edited by Patrick (edited 08-20-2022).]

DanMFiero88 AUG 20, 06:58 PM
Thanks again, Patrick. It’s interesting that you mentioned “choke” because that’s exactly where I would have gone with a carburetor.
theogre AUG 20, 08:29 PM
skip other testing, worse replacing parts, until test fuel pressure.

Need a gauge set AND TBI Test Adapter. see https://www.fiero.nl/forum/Forum2/HTML/146121.html
allowed is 9-13 PSI...
BUT...
If low, even above low allow = 9psi, then very likely fuel pump or soft hose attach to output to steel line is "bad."

Problem seems that even if both are "good," GM used plastic clamps on the rubber and fails to seal 30 years later. I don't think the clamp are bad but "rubber" get softer and clamps just hold hold.

If true likely need 3/8" of intank line not 5/16" used by most and clamps that handle 3/8" soft line. see https://www.fiero.nl/forum/Forum2/HTML/146240.html J30R10 intank fuel hose.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Patrick AUG 20, 09:10 PM

quote
Originally posted by theogre:

skip other testing, worse replacing parts, until test fuel pressure.

Need a gauge set AND TBI Test Adapter.



I didn't want to mention checking fuel pressure in this case as it's such a nuisance testing fuel pressure on a duke.

It's even more difficult to sort issues out on this duke as it's an '88.

Is there an "easy" way to test/check the MAT and CTS on a '87-'88 duke? On an '84-'86, WinALDL could be used.

[This message has been edited by Patrick (edited 08-20-2022).]

DanMFiero88 AUG 21, 08:16 AM
Thank you Ogre and Patrick. I will check the fuel pressure but I will be shocked if it is too low. As part of the restoration process between Oct-Dec last year, I replaced the fuel sending unit. I installed a fuel pump for a Buick Grand National in the unit.