Fuel Injector Problems - ‘85 (Page 1/1)
williamwestmo APR 20, 02:17 PM
I recently picked up a 1985 Fiero 2M4 SE with a 5 speed as a project. I was told the fuel pump needed to be replaced and the car had not been driven in 15 years due to the passing of the driver (the most recent owner’s father, who bought the car new in ‘85). The car is completely intact with only 63k miles and was an excellent find, but fuel issues plague it. After dropping the tank and doing a vinegar clean for the rust and replacing the sending unit, the fuel pump was having problems. In the name of getting the car to run on its own I purchased a 4-7 PSI in-line fuel pump (https://www.amazon.com/dp/B06ZZVDZG3/ref=cm_sw_r_cp_api_i_AK29DB172R5C3ZX2WA5Q) instead and wired it to the stock fuel pump wiring. The fuel pump comes on with the key as it is supposed to and pressurises the system. Once cranking the injector only dribbles out fuel unlike it should. After taking a 12v 2A battery tender and connecting it straight to the injector in sprayed fuel correctly and was more than enough to get the car past idle.
Is there something with the ECM causing this due to a lower fuel PSI or is this more likely bad wiring to the injector? I will test the voltage to the injector tomorrow and report back, but as of right now I am under the assumption the injector is perfectly fine and this is a ECM/Voltage problem.
NOTE: From what I understand the stock Fiero fuel pump outputs ~15PSI and this current pump is not long term, but it should be sufficient for at least an idle and >2,000RPM.
Patrick APR 20, 03:16 PM

quote
Originally posted by williamwestmo:

In the name of getting the car to run on its own I purchased a 4-7 PSI in-line fuel pump



Even if the engine idled, I doubt you'd be able to get the car moving. What is the actual fuel pressure you're getting?

When I was having issues with my duke's fuel pressure years ago (chronicled Here), it would barely run with 4 PSI of fuel pressure. It needs to be 9-13 PSI.

Did you drop the tank, knowing the car had fuel pump problems, and not replace the fuel pump?

What condition was the short piece of hose in which was connected to the fuel pump? It eventually rots/splits. If this is what's happened with yours, the inline pump will just be sucking air. The hose would need to be replaced with the proper submersible hose.

[This message has been edited by Patrick (edited 04-20-2022).]

olejoedad APR 20, 03:43 PM
As suggested, put the stock pump in it.
williamwestmo APR 20, 11:10 PM

quote
Originally posted by Patrick:

What is the actual fuel pressure you're getting?




Surprisingly, 8PSI at the injector


quote
Originally posted by Patrick:

Did you drop the tank, knowing the car had fuel pump problems, and not replace the fuel pump?




The entire fuel system needed a revamp, all rubber lines were replaced, the sending unit was toast and was replaced with a *near* matching replacement, fuel pump included. We were having issues with the fuel pump though (stock, but new) so an inline pump was added just outside of the fuel tank. I am absolutely certain there is enough fuel pressure to the injector for the car to idle, and honestly, drive. The problem is the injector is not spraying all that fuel it has to it, and is only trickling fuel, as if it is clogged. After putting power directly from the injector from a non-car source it sprays like it is brand new, with more than enough fuel (to the point it actually bogs the car with the throttle not wide open)

I am more or less curious as to whether this could be caused by the ECM, as this is not a permanent setup, but should be sufficient for running unless something is not as it seems. I got 11.7V to the injector with a resistance of 1.8Ohms (which seems low to me, though I am not familiar with single fuel injector resistances)
williamwestmo APR 21, 01:36 AM
UPDATE: The issue has been solved! I normally work with older cars and didn’t think about connecting the MAF. There was also a vacuum line or two disconnected, which seems to have fixed the issue. Car idles and revs fine now, so I can rest easy knowing it at least runs on its own. I appreciate the help guys and I’ll probably be back as I sort out the issues on this Fiero.