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

WARP TEN · 08-23-2022

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%20W...0Awakening.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 · 08-23-2022

Quote:

Originally Posted by 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%20W...0Awakening.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 · 08-23-2022

Quote:

Originally Posted by racerns

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 · 08-31-2022

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 · 08-31-2022

Quote:

Originally Posted by 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/29128199537...mis&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 · 08-31-2022

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 · 08-31-2022

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 · 09-01-2022

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 · 09-01-2022

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.

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

08-23-2022	#2
WARP TEN Join Date: Apr 2007 Location: Lake Bluff, IL Posts: 2,049	Re: Reviving a 90, Miss leads to multiple issues 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%20W...0Awakening.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 __________________ 2016 Long Beach Red Z06 #10281 "POPS Z" 1995 Polo Green #409 "WARP TEN"--Haibeck 350/510 package, 4.10s, Hurst, Stock Exhaust with QTP Cutouts --Sold but still running strong 1993 Quasar Blue #161 "HIL KING" --Sold but still running strong, now with more than 120,000 miles 1967 Marlboro Maroon/Saddle Corvette Coupe 300 hp/4-spd --Sold a long time ago ZR-1 Net Registry Founding Member #95 NCM Lifetime Member Favorite Quote--Attributed to Mickey Thompson: "Too Much Horsepower is Almost Enough" Last edited by WARP TEN; 08-23-2022 at 10:38 AM.

08-31-2022	#5
dredgeguy Join Date: Aug 2012 Location: Ellicott City, MD Posts: 1,638	Re: Reviving a 90, Miss leads to multiple issues 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. __________________ Charlie __________ Dredgeguy WAZOO Member 1992 Bright Red/Black ZR1 #246 Dana 4:10 gears Polished LT5 by Haibeck Polished Fikse FM5's with Michelin Pilot Sport 2 Stainless Works headers and cats with Corsa

08-31-2022	#7
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,681	Re: Reviving a 90, Miss leads to multiple issues 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. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

08-31-2022	#8
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 881	Re: Reviving a 90, Miss leads to multiple issues 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 __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

09-01-2022	#9
Corvette95 Join Date: Jan 2006 Location: Decatur, AL Posts: 1,107	Re: Reviving a 90, Miss leads to multiple issues 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. __________________ Corvette95 Registry and Forum (*************) 1989 C4 Conv Wht/Gry Auto Hardtop Top Flight SOLD 1995 C4 Coupe Purple/Blk 6 Speed 1989 C4 Conv Wht/Red Auto SOLD 1996 C4 Conv Black/Tan Auto SOLD 1994 C4 Coupe Wht/Blk SOLD 1995 C4 ZR-1 White/Gry #278 Dual Dunn Head SOLD 1986 C4 Coupe Black/Red 4+3 SOLD 1990 C4 ZR-1 Red/Red #0454

09-01-2022	#10
phrogs Join Date: Jul 2004 Location: Kalamazoo MI Posts: 1,746	Re: Reviving a 90, Miss leads to multiple issues 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. __________________ JOHNNY P Currently own 90 ZR-1 #845 DRM 500 engine package 90 #226 Parts car Hit me up if you need anything.