1990 ZR-1 Issues

[frantinoro]

Hello,
I got my zr-1 and it never ran right, but after sitting for a few months it's a lot worse. It misfires out the left bank, smells lean, and genuinely runs horribly. Before I parked it I put in new injectors, coils, plugs, and plug wires, so I can't tell much from the plugs, but they look fine. I resealed the IH and all the vacuum lines for the secondaries, and when jumpering them they work as they should. My only issue I've found so far is I'm only getting 38 psi at idle, and 35 at wot. Both pumps are suburban pumps and new, new o2s as well, and both pumps work when jumpered. I contacted Phil who rebuilds the FPRs and he doesn't think it's my fpr because it doesn't leak. Does anyone else have anything I can test? Thanks again

[A26B]

One obvious problem is your low fuel pressure.

Have you performed the static test (key on, engine off) individually, for each of your fuel pumps?

If the static test is still low, I suggest you remove the Fuel Pump Sender Assembly & inspect all the hoses & components for breaks or leaks.

If the inspection didn't reveal any leakage, then it may be one or both of the fuel pumps. Observe static fuel pressure. With Key on, Engine off, pressurize the fuel rail, turn key off and see how long it takes for the pressure to bleed off. Fast bleed down would indicate fuel pump check valve failure.

If the static test result is within spec, then disconnect the vacuum line from the FPR & plug the vacuum line. Start engine & observe the pressure. If the pressure is low again, then the regulator is at fault.

[frantinoro]

Hey. Static fuel pressure not running was around 45-50, can't remember off the top of my head, but it did decrease when running. When removing the vacuum line while running, the psi also did jump up to around there.

[Paul Workman]

Originally Posted by frantinoro

Hey. Static fuel pressure not running was around 45-50, can't remember off the top of my head, but it did decrease when running. When removing the vacuum line while running, the psi also did jump up to around there.

Well, "normal" static pressure with low dynamic pressure speaks to a DELIVERY issue - a blockage somewhere.

First up: FUEL FILTER or fuel lines come to mind. I'd put the pumps and the "Y" and connectors on the back burner for now i.e., not indicated by symptoms, but part of the 'delivery' system.

[frantinoro]

I did it a few months ago; but I'll do it again

[frantinoro]

So I blew out the lines, warrantied my pumps and put another new filter in. Now at WOT I'm getting 50 psi and 40 psi idle. What to test next?

[frantinoro]

To clarify, it's still a little rough at lower rpms, and will not go into full power Mode. I jumped C17 and they opened just fine. No leaks, pump runs every few minutes and I've tested everything under the plenum. Blew smoke into all the hoses going into the plenum and not a single leak, just some smoke coming out of the air filter

[frantinoro]

Any idea what to test next? I hooked up my scanner and the left bank is running lean (BLM iand int Anmrr at around 150)

[Ccmano]

Have you checked for codes? Easy to do with a paper clip if your don’t have a scanner. Electronic issues will usually throw codes.

It’s also possible the accordion air bridge connector between the air filter housing and the air horn is collapsing at full throttle, giving the impression of no secondaries, had it on mine. Remove it and drive it without it in place. If that’s the case you’ll feel the difference immediately.
H

[frantinoro]

Thanks for the reply. The accordion has been replaced with a Jerry's gaskets one. I do have a scanner and it throws no codes, but has thrown a lean code left bank a few times. My BLM and INT on the left side is around 150 as well, and the right side stays around 130. I jumpered all the injectors and heard a click for every one too. Although my scanner is saying the vacuum at idle is 0 kpa, but I'm not sure if the car should be giving me a reading for that. TPS and MAP voltages seem fine. O2 sensors are new and cycling like they should in the scanner, although they do not read evenly, and cycle slightly offset, I could not find anywhere if that was normal.