I have this 87 GN, and i think the fuel pump is going, here’s what its doing.
1. When it first starts, it idles high, then almost stalls, then jumps up (about 4000) then almost stalls, and repeated this process for about 5 minutes (fuel pressure problem)
2. at idle, the rpms of the engine serge about 50-100 rpms, it doesn’t stay consistent.
3. yesterday pulling up to a signal, it made a one quick popping sound and almost stalled
i was told to check my O2 sensor, my IAC and my TPS, i haven’t checked my o2 yet and the scan tool that i borrowed from my friend doesn’t seem to have an IAC on it... i checked the TPS and the readings were (at idle) 0.42 and at WOT 4.30, and i read on here that the TPS at WOT should be between 4.55 and 4.85.
i don’t know if anyone knows, but any help i would greatly appreciate, i don’t really want to be pushing about 15psi of boost and then all of a sudden lose fuel pressure, I’m pretty sure the engine wouldn’t appreciate that. and if you know anything about fuel pumps, i was wondering if you have heard anything about Warblo 307 pumps... i heard they are good for GN's. thanks again for any help.
Simple test ... put a fuel pressure gauge on it ... tape it to the windshield and take a drive and watch fuel pressure (and watch it when the odd idle stuff happens).
Should be pretty obvious when it happens ... you can get a cheapo gauge for this purpose from J.C. Whitney (about $25, last I looked). Splice 2-3 feet of HIGH PRESSURE FUEL INJECTION RATED hose to it, screw it onto the end of the fuel rail, then tape it to the windshield ... should tell a lot.
As far as Walbro pumps .. well proven (both the 307 and the 340). Also, Red Armstrong (Quad Air) sells his "XP" pump that's very good also.