Reviving a 90, Miss leads to multiple issues - Page 2 - ZR-1 Net Registry Forums

racerns · 09-20-2022

Update on this. Thanks for all the advice. So I did replace all the injectors and coils. Pulled all the plugs and ohm'd the wires and they were fine. Checked vacuum lines and cleaned up under the plenum and put it back together. It ran much better with a smoother idle, but still had an off idle stumble/miss. At this point I hadn't replaced the pumps yet. Both pumps individually made +50 psi and amp draw seemed fine, but pressure bled down very fast. I did go ahead and changed them. I did wipe out the tank and there was a good bit of corrosion on the assembly that I cleaned off. It was one of the pump check valves that was leaking back. The y fitting and hoses were fine but I did replace all the clamps. I put it back together and after priming them with the pump test connection it fired up and ran fine. The off idle stumble was gone. Not sure how the pumps caused that issue? It is possible that low battery voltage contributed to the stumble as I had to charge the battery in between attempts.

Now that it running well I was going to turn my attention to some cosmetic issues and high tach reading, but the heater core had other thoughts. It started dripping in the pass footwell. I have just bypassed it for now. I am sure that will a major pain in the *** to replace.

preshenne · 09-29-2022

Just went thru the pump/sender replacement on my 95 ZR-1. ZR1-Dan on ebay has an excellent LT5 single pump conversion available. Plug and play tank unit. Pull one ECM pin to power secondary pump circuit full time, as described by Marc Haibeck. Works great. Uses a Racetronix Pump with about 50% more capacity than the two OEM pumps together. So far so good, motor pulls well. A bit pricey, but it literally drops in. All the "fits ZR-1" pump/sender units on ebay seem to be base model C4 single pumps. seems likely that these will not have sufficient fuel capacity for high ZR-1 fuel demand operation.

09-20-2022	#11
racerns Join Date: May 2022 Location: Smithfield VA Posts: 3	Re: Reviving a 90, Miss leads to multiple issues Update on this. Thanks for all the advice. So I did replace all the injectors and coils. Pulled all the plugs and ohm'd the wires and they were fine. Checked vacuum lines and cleaned up under the plenum and put it back together. It ran much better with a smoother idle, but still had an off idle stumble/miss. At this point I hadn't replaced the pumps yet. Both pumps individually made +50 psi and amp draw seemed fine, but pressure bled down very fast. I did go ahead and changed them. I did wipe out the tank and there was a good bit of corrosion on the assembly that I cleaned off. It was one of the pump check valves that was leaking back. The y fitting and hoses were fine but I did replace all the clamps. I put it back together and after priming them with the pump test connection it fired up and ran fine. The off idle stumble was gone. Not sure how the pumps caused that issue? It is possible that low battery voltage contributed to the stumble as I had to charge the battery in between attempts. Now that it running well I was going to turn my attention to some cosmetic issues and high tach reading, but the heater core had other thoughts. It started dripping in the pass footwell. I have just bypassed it for now. I am sure that will a major pain in the *** to replace.

09-29-2022	#12
preshenne Join Date: Jul 2022 Location: Hilton Head Island, SC Posts: 12	Re: Reviving a 90, Miss leads to multiple issues Just went thru the pump/sender replacement on my 95 ZR-1. ZR1-Dan on ebay has an excellent LT5 single pump conversion available. Plug and play tank unit. Pull one ECM pin to power secondary pump circuit full time, as described by Marc Haibeck. Works great. Uses a Racetronix Pump with about 50% more capacity than the two OEM pumps together. So far so good, motor pulls well. A bit pricey, but it literally drops in. All the "fits ZR-1" pump/sender units on ebay seem to be base model C4 single pumps. seems likely that these will not have sufficient fuel capacity for high ZR-1 fuel demand operation.