Reviving a 90, Miss leads to multiple issues

[racerns]

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/291281995379?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=j45bwt1nToi&sssrc=2349624&ssuid=XoZFzjyUTGG&var=&widget_ver=artemis&media=COPY

Neil S

[WARP TEN]

There are more knowledgeable folks out there than me who will provide more substantive and detailed answers to your questions, but '90s all need the injectors replaced as they are not compatible with ethanol-laced gasoline. Check with Jerry's Gaskets for injectors. There are quite a few threads here that you can search for about injectors, coils, fuel pumps, plenum pulls and other things, as well as on generally reviving a lightly used ZR-1, plus a good presentation from Marc Haibeck on the subject: http://www.zr1specialist.com/HAT%20Web/presentations/The%20Great%20Awakening.pdf. It sounds like you are knowledgeable and are on the right track to fixing your problems. Do you have a factory shop manual? If not, it it an excellent idea to get one. Hope you get your beast running well soon! --Bob

[racerns]

There are more knowledgeable folks out there than me who will provide more substantive and detailed answers to your questions, but '90s all need the injectors replaced as they are not compatible with ethanol-laced gasoline. Check with Jerry's Gaskets for injectors. There are quite a few threads here that you can search for about injectors, coils, fuel pumps, plenum pulls and other things, as well as on generally reviving a lightly used ZR-1, plus a good presentation from Marc Haibeck on the subject: http://www.zr1specialist.com/HAT%20Web/presentations/The%20Great%20Awakening.pdf. It sounds like you are knowledgeable and are on the right track to fixing your problems. Do you have a factory shop manual? If not, it it an excellent idea to get one. Hope you get your beast running well soon! --Bob
Thanks for the info. I do have the factory shop manual. I am pretty much set on getting new injectors just wondering if anyone had used the Bosch set from Motorman that I linked. Probably going to go with the Performance Electric pumps for replacement and not sure about coils.

[A26B]

Thanks for the info. I do have the factory shop manual. I am pretty much set on getting new injectors just wondering if anyone had used the Bosch set from Motorman that I linked. Probably going to go with the Performance Electric pumps for replacement and not sure about coils.

a brief synopsis of the general trend among ZR-1 owners over the last 15 yrs or so, regarding LT5 injectors.

1. There are two(2) predominate brands of new injectors, ACCEL & FIC. Both have been used successfully. Accel doesn't have customer service for injectors, FIC does. Accel injectors used to be made in USA, now made in China. I don't know when the change occurred.

2. "Rebuilt" injectors are sketchy. There have been bad reports and a few good reports. Regarding good reports, I don't recall any of the good report posters ever posting later about whether they failed or not after some period of time.

3. Re: cleaning & testing injectors. The cost of the service varies widely as I suspect the quality of service does. Most of the sites I have seen and reports from customers, place the cost of cleaning & testing to be about 75% of the cost for new injectors. For the 90-92 models with original injectors, it's a total waste of money. The solenoid windings are not ethanol tolerant and WILL fail eventually from the use of ethanol blended gasoline. 93~95 models are ethanol tolerant. Jerrys Gaskets has sold several hundred sets of FIC injectors and virtually all (95%+) were for 90~92 models, as one would expect.

If you have a 90~92 model with original injectors and plan to keep it for the long haul, I recommend buying a complete set of new injectors.

Hopefully other will add there opinions to give you a good perspective on replacement of injectors.

[dredgeguy]

I have 2 new in the box Performance Electric pumps if your interested but suggest you go with Delphi pumps from RockAuto as they have the ridge on the end of the port so your hose clamp has something to clamp down against. The Performance Electric does not and I had my hose slip off twice in 3 years.

[Corvette95]

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/291281995379?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=j45bwt1nToi&sssrc=2349624&ssuid=XoZFzjyUTGG&var=&widget_ver=artemis&media=COPY

Neil S

To address the fuel injectors, I do completely get it for the price but if you want to keep this car, spend the extra two hundreds for the FIC's from Jerry. His products are top notch and your gonna need him a lot in the near future.

[XfireZ51]

I transitioned to FIC injectors after having Accels for 10+ years. The FICs are more specific to the LT5 application rather than the Accels which are replacements for 5.0 Mustang GT motors.
My recommendation on replacement of injectors is to get them flow tested independently and then flow match the individual cylinders based on those results. Don?t take anything for granted. That preliminary step will make a significant difference in how smoothly your motor runs.

[Young1]

First things first. You must be able to build and hold fuel pressure with each pump. If you make 50 ish psi with each pump but does not hold.
A. Bad check valve in a pump
B. Cracked Y connector in tank
C. Cracked fuel line or loose clamp in tank.
D. Leaking injector

IMO. Replace the pumps, lines, clamps in the tank.
Get fuel p

[Corvette95]

Be sure to get Phil's fuel pressure regulator and Carters aluminum Y-Connector for inside the tank. Also, be sure to note the orientation of the fuel strainers as they need to go back on the way they came off (assuming they are OEM). Its only a big deal if it's your first time pulling the LT5's Fuel pressure sender and pumps. My highly suggested tip it to pump out every last drop of gas you can with a pump of your choosing...manual, siphon, ( I use a remote battery power fuel pump) and when you pump all you can out of the tank, take something super absorbent but doesn't fall apart when exposed to gas ( I use baby diapers) absorb every last drop of liquid in your tank then WIPE the inside of the fuel tank clean (no additional cleaner usually needed) . Discard old fuel, even if it looks good, and refill to top with good gas ( I use non ethanol only - my preference) . Keep your tank fuel full as air causes rust on the sender and pumps. You will likely find small particles all over the bottom of the tank and fuel pickup - will look like gravel and worse, if it sat with low fuel, the whole sender and tank can be covered with rust. ( Yes, tank is rubber lined but will still rust through with low fuel and high condensation.

[phrogs]

I just did a pressure test on my new single fuel pump conversion and at the fuel rail it pumps up nice to around 50Psi but then falls off until you start the car.

If you took out the fuel pumps and the assembly wasn't all corroded id be surprised.

[racerns]

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]

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.