yorxs Posted April 1, 2013 Report Share Posted April 1, 2013 I'm starting to suspect the fuel pump is going out on my 93 GP 3.4. I replaced the fuel filter this weekend and while I was under the car I didn't see a schrader valve on the fuel rail. Am I missing the location or do I need some type of t-connector to do this test? Quote Link to comment Share on other sites More sharing options...
94 olds vert Posted April 1, 2013 Report Share Posted April 1, 2013 It's located near the plenum fuel line. It should have a black cap on it. Quote Link to comment Share on other sites More sharing options...
yorxs Posted April 6, 2013 Author Report Share Posted April 6, 2013 Plenum? Would this be in the engine bay then? Also I don't see fuel pressure specs for an LQ1 with MPFI only PFI and SFI at 40 to 47 psi, would MPFI be the same? Quote Link to comment Share on other sites More sharing options...
55trucker Posted April 6, 2013 Report Share Posted April 6, 2013 You need to pull up the engine cover, under it you can see the fuel rail that supplies the front bank, at the far right side where the rail makes a 90 degree to go around the front side of the engine you'll find the schrader valve there. The fuel thru the rail when the engine is running can be from 40 to approx 48 lbs. Quote Link to comment Share on other sites More sharing options...
yorxs Posted April 7, 2013 Author Report Share Posted April 7, 2013 Testing fuel pressure now but getting 0psi at key on but the car runs. Is 0psi even possible or am I just way off the mark? Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted April 7, 2013 Report Share Posted April 7, 2013 (edited) 0psi is no possible to obtain and still have car run. With the key on, pump will prime, but then pressure will bleed off. Best to test with motor running. Edited April 7, 2013 by 19Cutlass94 Quote Link to comment Share on other sites More sharing options...
yorxs Posted April 7, 2013 Author Report Share Posted April 7, 2013 Should've clarified in the last post, 0psi at key on and while ruinng. If I depress schrader valve on the fitting to the guage it will squirt gas at key on, just not sure its 40+ psi or not, just can't get the guage to read anything. Also how does one determine if the pump or the fuel pressure regulaor is the cause of low pressure? Quote Link to comment Share on other sites More sharing options...
55trucker Posted April 7, 2013 Report Share Posted April 7, 2013 What are you using as a gauge to test the rail's pressure? Quote Link to comment Share on other sites More sharing options...
yorxs Posted April 19, 2013 Author Report Share Posted April 19, 2013 Alright, tested before the pressure regulator, I'm getting 45 to 46 psi at key on and about 39 to 40 with engine is running. These numbers look good, but still 0psi after regulator so I replaced it and the Plugs, PCV and O2 sencsor since the is plenum off. I still get an idle with lots of vibration, but a steady needle on the Tach. Car is slow to accelerate but seems to surge up to speed at about 35mph+. The engine has never stalled on me and the car starts right up. Anyone had sucess with similar symptoms? Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted April 19, 2013 Report Share Posted April 19, 2013 sounds like good fuel pressure. sounds like something else is going on though. Quote Link to comment Share on other sites More sharing options...
55trucker Posted April 19, 2013 Report Share Posted April 19, 2013 Hmmmm........next step, at idle, when this situation occurs, shut down the engine, pull the plugs out, and look for any plugs that are wet or discolored (not tan). You said you replaced the plugs?....what about the plug wires? If you find that they are all as they should be, put them back in, fire the engine, when this situation occurs (at idle), one by one pull off the plug leads and note any LACK of change in the engines idle. start there, report back. Quote Link to comment Share on other sites More sharing options...
yorxs Posted April 29, 2013 Author Report Share Posted April 29, 2013 Cylnders 1 and 4 seemed to have the least effect on the idle when removed. Tracing the plug wires back to the coils, they just so happen to be fed from the same coil pack. Looks like I finally found the culprit! I'd like to remove each pack individually so I have an easier time marking which wire goes where. But its looking like the assembly they bolt to has to come out thus I need to remove all six wires at once. Kind of a pain to mark everything when you can't see shit down there. Advice anyone? Quote Link to comment Share on other sites More sharing options...
jman093 Posted April 29, 2013 Report Share Posted April 29, 2013 You can remove an individual coil. Remove the 2 small bolts going through the coil. They're like 4mm or something. It will then pull off of the ignition module. Quote Link to comment Share on other sites More sharing options...
55trucker Posted April 29, 2013 Report Share Posted April 29, 2013 Cylnders 1 and 4 seemed to have the least effect on the idle when removed. Tracing the plug wires back to the coils, they just so happen to be fed from the same coil pack. Looks like I finally found the culprit! I'd like to remove each pack individually so I have an easier time marking which wire goes where. But its looking like the assembly they bolt to has to come out thus I need to remove all six wires at once. Kind of a pain to mark everything when you can't see shit down there. Advice anyone? The replacement of the coils is easier done with the rad fan assembly removed. It's up to you whether you want to tackle the coils with it in, personally I don't mind taking the time to make the job easier, as Jesse said the coils can be removed individually. Quote Link to comment Share on other sites More sharing options...
yorxs Posted May 1, 2013 Author Report Share Posted May 1, 2013 So trying a 5mm, 6mm and 1/4" and nothing seems to really fit. If this is a 5.5mm any ideas where to get a socket? Harbor Freight appears to be a bust. Quote Link to comment Share on other sites More sharing options...
yorxs Posted May 1, 2013 Author Report Share Posted May 1, 2013 Nevermind I found a set there, cheap too! Quote Link to comment Share on other sites More sharing options...
yorxs Posted May 1, 2013 Author Report Share Posted May 1, 2013 Car is fixed, coil 1/4 was the problem. Talk about making an easy fix a tough one. Between the metal hose blocking the way and the starter power blocking the way one can only wonder if the engineers at GM are assholes or stupid. Quote Link to comment Share on other sites More sharing options...
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