High fuel pressure, high idle, fuel meter cover? (Page 1/1)
Saggy SEP 29, 11:44 AM
I'm trying to figure out what's wrong with my Fiero. It's the 84 4 speed se with the 2.5 duke. I've got high fuel pressure at 19 psi should be 9-13 psi. When I start up the car the idle bounces around 2.5-3.5k once it warm up enough to move the needle it idles around 1k-900rpm. It has small surges and drops in its idle, but never so much I would worry about drivability. I was running through a test procedure from alldata, and I was told to replace the fuel meter cover. I have no clue what that is, let alone where. I haven't been able to find any results online for it. I'm looking for as much advice as I can find about this, as I've been trying to fix this problem for months.
Patrick SEP 29, 01:18 PM

quote
Originally posted by Saggy:

...was told to replace the fuel meter cover. I have no clue what that is, let alone where.



I suspect it has something to do with the fuel pressure regulator.
theogre SEP 29, 03:30 PM
High Pressure then First thing to check is:
Check the gauge... Many gauges are not very accurate reading bottom or top off scale and most shop fuel gauges reads 0 to 100+ PSI.
I change the gauge on one test set to read 0 to 20 or 30 PSI for use w/ Carbs and Low Pressure EFI used by most 300 and 700 series TBI. (Many carbs use only 2 - 5 PSI Max. or fuel will flood the bowl.)

Then check return line damage. ANY pinching or crushing in that line can cause high pressure.

Pull return line and should easy blow air.
return can be block w/ crap or or crush where you can't see.
If tank or engine was pulled for any reason... vent and return can be connected wrong. Vent line is very redistricted at the tank end to prevent liquid fuel getting at EVAP "can."
If fuel pump was replaced, can be wrong pump... Pumps for Port Injection = made for high pressure and often higher volume and often "peg the reg" for TBI engines and can't dump fuel fast enough cause high pressure problems.

Note that ECM can have problems too cause engine running like crap or even setting 44 45 and other codes.

regulator can have problem and get block w/ crap in the feed line etc. You have 300 series TBI covered hundreds of doc's by GM and many others telling how it works and how to fix...

If TBI needs taken apart... first get a "rebuild kit" that have most parts/seals/etc.

------------------
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

[This message has been edited by theogre (edited 09-29-2021).]

buddycraigg SEP 29, 07:34 PM
How are you testing the fuel pressure?
The 4 cylinders do not have a test port.
theogre OCT 01, 01:41 AM

quote
Originally posted by buddycraigg:
How are you testing the fuel pressure?
The 4 cylinders do not have a test port.

true for this engine. See my Cave, TBI Test Adaptor
Saggy OCT 01, 08:36 PM
I tested the pressure by simply disconnecting the fuel line at the throttle body, and hooking a fuel pressure tool my collage has to both ends. Good chance this tool was off, because the collage is terrible with tool maintenance, although it was the fancy snap-on brand. I do get a check engine light occasionally when driving on highways. When I restart the car, the code disappears. The car also has some sort of gearing reduction, I imagine it's in the differential so it runs a higher rpm on highway than it should. It can sound a little clunky sometimes. I have also learned I do not have the EGR valve anymore, is it possible that could cause issues? I have replaced the fuel pump, but changing the pump didn't change how the engine ran.
buddycraigg OCT 08, 08:21 PM
If you are connecting the fuel pressure tester to the line coming from the fuel pump, then you do not have the pressure regulator as part of the equation. So you will be getting a way higher reading than what you should see.

I suggest you start a new thread with a different question. State what the symptom is and go from there.

[This message has been edited by buddycraigg (edited 10-08-2021).]