Georgia Fiero Club Forum

All Things Fiero => Tech Tips, Tech Questions => Topic started by: montegut on July 11, 2021, 06:29:48 pm

Title: Surging, dropping fuel pressure
Post by: montegut on July 11, 2021, 06:29:48 pm

I have had a surging, hunting idle problem with my 87 GT for years that recently has gotten worse.  It has gotten to the point where it will stall when stopped with the AC on. Over time I have tested or replaced all potential causes with no luck. The only thing I hadn't tested was the fuel pressure. Today it was 40# when the fuel pump primed and then within seconds dropped to 31#. After 10 minutes it was 28#.  So next weekend I plan to pull the injectors and send them out to be tested and  reconditioned.

I also plan to replace the fuel pressure regulator and will order and install Rodney's stainless vacuum lines.  Does this sound like a reasonable plan? Anything else I should check or replace "while I am in there?"

Finally any recommendations on fuel injector services?

Thanks

Title: Re: Surging, dropping fuel pressure
Post by: Fierofool on July 11, 2021, 07:19:27 pm

Disconnect the cold start injector at its switch, top right front of the lower manifold before you do anything else.  It could be stuck and leaking  If you still get the leakdown, you're probably on the right track.  Does it have a rich exhaust when idling?  If it does, it could be an injector.  If not, it's probably the regulator. 

The regulator at The Fiero Store is $72 plus shipping and handling.  AutoZone has it for $87 with no shipping and handling.  Same number for the Fiero V6   Part #800-122 SKU # 79671
https://www.autozone.com/fuel-delivery/fuel-pressure-regulator?filterByKeyWord=fuel+pressure+regulator&fromString=search&isIgnoreVehicle=false&model=fuel

Title: Re: Surging, dropping fuel pressure
Post by: TopNotch on July 11, 2021, 07:47:15 pm

When's the last time you changed your fuel filter?

Title: Re: Surging, dropping fuel pressure
Post by: GTRS Fiero on July 11, 2021, 07:55:32 pm

A agree on the regulator.  If it can't maintain pressure, that is the first thing to check.  Also on the cold start injector.

Title: Re: Surging, dropping fuel pressure
Post by: GTRS Fiero on July 17, 2021, 01:27:40 pm

Any progress?

Title: Re: Surging, dropping fuel pressure
Post by: montegut on July 18, 2021, 12:27:03 am

Unfortunately no. Been crazy busy. Got a pressure regulator from Rock Auto Thursday and hope to install tomorrow. When I get something done, I will post.

Title: Re: Surging, dropping fuel pressure
Post by: montegut on July 18, 2021, 12:29:17 am

Will test the cold start injector like Charlie advised before tearing anything down.