Reviving a 90, Miss leads to multiple issues - ZR-1 Net Registry Forums

racerns · 08-23-2022

So this is my first post, but I have been lurking and reading for a while. The car is a '90 with 45K miles. It was originally my father's which he bought new and I have owned it since 2012. Unfortunately it had been sitting outside under a cover sitting mostly since 2014. I have just started reviving it.

I did the basics of new battery, draining fuel, changed the oil, and such. It started up and at first seem ok but developed a miss and knock. It got worse as the engine warmed up. I checked fuel pressure and at key on it went to 52psi but almost immediately drops off quickly. I checked both pumps individually and both worked but seem to be only pulling 3A each. I suspected that it was bad/leaking injector since they had been sitting so long and appeared to be stock units. I pulled the plenum and pressurized the fuel to find that the injectors were not leaking to cause the fuel pressure drop. I did cold ohm check all the injectors (at the connector) and 2 of them were out of range with reading just below 10 ohms. I then checked the ignition coils and wires (relatively new mile wise msd plug wires). The wires were fine but one coil was completely open between the secondaries. So I am sure this is the biggest cause of the miss, but I still have the fuel pressure drop issue. I would guess this points to a fuel pump check valve? Are these check valves internal to the pump? It seems changing the pumps are relatively inexpensive. Last is the injectors, as they do seem to be stock and 2 are reading bad I think the smart thing is to change them?

I will be getting 4 new coils and probably plugs. So any thoughts on the the fuel pumps or my diagnosis? Also should I replace the alternator while I have the plenum off? Don't think it is bad, just +30 years old.

Also, anyone bought these injectors?
https://www.ebay.com/itm/29128199537...mis&media=COPY

Neil S

08-23-2022	#1
racerns Join Date: May 2022 Location: Smithfield VA Posts: 3	Reviving a 90, Miss leads to multiple issues So this is my first post, but I have been lurking and reading for a while. The car is a '90 with 45K miles. It was originally my father's which he bought new and I have owned it since 2012. Unfortunately it had been sitting outside under a cover sitting mostly since 2014. I have just started reviving it. I did the basics of new battery, draining fuel, changed the oil, and such. It started up and at first seem ok but developed a miss and knock. It got worse as the engine warmed up. I checked fuel pressure and at key on it went to 52psi but almost immediately drops off quickly. I checked both pumps individually and both worked but seem to be only pulling 3A each. I suspected that it was bad/leaking injector since they had been sitting so long and appeared to be stock units. I pulled the plenum and pressurized the fuel to find that the injectors were not leaking to cause the fuel pressure drop. I did cold ohm check all the injectors (at the connector) and 2 of them were out of range with reading just below 10 ohms. I then checked the ignition coils and wires (relatively new mile wise msd plug wires). The wires were fine but one coil was completely open between the secondaries. So I am sure this is the biggest cause of the miss, but I still have the fuel pressure drop issue. I would guess this points to a fuel pump check valve? Are these check valves internal to the pump? It seems changing the pumps are relatively inexpensive. Last is the injectors, as they do seem to be stock and 2 are reading bad I think the smart thing is to change them? I will be getting 4 new coils and probably plugs. So any thoughts on the the fuel pumps or my diagnosis? Also should I replace the alternator while I have the plenum off? Don't think it is bad, just +30 years old. Also, anyone bought these injectors? https://www.ebay.com/itm/29128199537...mis&media=COPY Neil S