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I purchased a 1991 L98 hardtop.
I have used this website as a resource over the past year. We purchased an 89 Iroc for my son and it has been tons of fun. I decided to purchase a left for dead car to resurrect to do some events with my son. His car was just updating maintenance items. My car is a project so with that. Where do I start? I have no idea of the engine and suspect i will be rebuilding it. I have not worked on tuned port or injected cars. Should i drain the tank and start with fresh gas? Will the injectors get damaged with stale gas? I suspect the car has sat for the past 10 years but is very original.
Thank you in advance for help and input.
sons 89 in original paint white 2nd owner car & the black 1991
You might start with the basics, check spark, compression and injector pulse.
with the car sitting with fuel that long everything from the pump to the regulator to injectors will need replacement.
You might start with the basics, check spark, compression and injector pulse.
with the car sitting with fuel that long everything from the pump to the regulator to injectors will need replacement.
thank you i just ordered a pile of that stuff. I’m going to hold off on injectors for now till i read a bit more and figure out what’s best. I dont want to do them till everything else is straight. I would like to chat with you as i will need to get a chip for the basic mods and my brother would like to get a chip for his car. Please pm me with your number and when is best to chat
Might chat with southbay fuel injectors on injectors. On an all stock l98 I like there delphi 22#hr. There D3 skinny ones will work but kinda noisy and I’ve seen some cars run slightly lean without tuning . I’ll send you a personal message.
If it hasn't run in that period, pull some spark plugs to check condition, and don't hesitate in applying some oil through the plug holes. 2-cycle oil is pretty good for this purpose. Obviously, get a fresh, reliable battery installed. You can crank the engine with the plugs removed to distribute oil, and possibly develop oil pressure in the system. Listen for unusual noises as well. Checking spark to the plugs during this is also a good exercise.
Drain whatever fuel you can, then add a quantity of the LOWEST octane fuel you can find, since it is more volatile. Ethanol can actually help in this instance. Stand by with a fresh fuel filter, or two. Operate the fuel pump and try to determine if pressure is being developed. If so, cycle the pump numerous times or power it with a jumper to flush lines back to the tank.
The original injectors might just get you started and running, even if they have some spray pattern or screen clogging problems. It would be discouraging to install fresh, new injectors and have them slugged with a handful of debris from the tank the first time it starts. If it runs without serious mechanical noises, it will be a good step.
Verify all the fluids. Don't overlook the brake fluid, which will eventually need to be replaced with the other fluids.
The photo shows an alarm system installed, and if there is also a remote start, don't be surprised if that has issues interfering with starting.
Here's the one I got a couple of years ago. '89 one owner all original IROC-Z LB9, MT, 22k miles. It sat for a while but got going easy. Here's what I did:
New gas, fuel filter change and seafoam treatment
New tires (they were factory original dry rot!!!!!!)
Fuel pressure + initial timing checks
Charging system check
Oil + filter change
Fluid checks
Drove it hard to make things that had to fail... actually fail. Not that hard but hard enough! Pretty much anything that had rubber it in failed.
Recorded some data stream for diagnostic SES light and stumbling on cold start using laptop and AFR gauge.
Engine bay clean-up
Undercarriage inspection and clean-up
Thorough inspection of about everything!
New air filters
New spark plugs, cap, rotor (wires were good)
New thermostat (was opening too soon)
Reman smog pump... was making a racket
New accessory belt (dry rot)
Thorough coolant flush
Throttle body coolant by-pass (little hose was leaking)
New front brakes (Powerstop Z26) and caliper maintenance
Complete rear brake disassembly + clean-up + lube + new cylinders (were leaking)
New brake fluid and clutch fluid
New braided brake hoses
Manual transmission oil replacement (Dexron III)
Speedometer cable leak fix
New engine rear main seal (leaking)
New clutch throw-out bearing (preventative)
Engine oil pan restoration (rust)
Repack front wheel bearings + new seals
New valve steam seals (was puffing smoke on cold start-up)
New struts/shocks (rear were shot!!!)
New suspension bushings all around (dry rot)
Steering linkage clean up, inspection and lubrification
Alignment
New hood struts
Rear end oil change + posi additive
Oil pressure fuel pump switch by-pass (fuel pump would stay on after shut down)
Reman MAF sensor (was causing issue and SES light)
New battery
Fog light casings restoration (rust)
Complete paint decontamination, inspection, assessment and enhancement. Paint is original.
Fixed a few rattles and T-Top adjustment
Interior was in immaculate condition.
Did not do compression test. It does not burn oil and 1/4 mile times are right on.
Added UMI Performance #2400-B subframe connector to protect chassis integrity. Some light crack had started on driver's B pillar (classic!)
I've been doing fuel filter changes every 500 miles with Seafoam treatment. The brown sediment is getting lesser. I am trying to avoid fuel tank removal and clean-up. I have a set of injectors in stock since it still has the OEM Multec. They have not failed yet!!!!
Did all work myself except welding subframe.
Car runs so much better than when I bought it. These things need a lot of TLC. Next will be A/C restoration. It failed after 1 year...Everything was factory original!!!!
I'm expecting master cylinder and clutch slave/master failure as well as injector failure. Radiator looks good. Water pump and power steering not leaking yet. ICM might fail... and many other things
'Sounds like a cool project. Let's see some pics...
well it needs a ton of work but its a great platform for what i want. I actually have a black 87 i picked up and its got a better body but just too big a project and that’s why i grabbed this. Quicker time to get it on the road
here is the 87 im going to sell to focus on the 91. Its a hot mess but a very solid body
The 91 is a little crustier but great never hit car one repaint and very tittle has been touched. It’s an l98 g80,gu5,j65 custom package 2 car.
Here's the one I got a couple of years ago. '89 one owner all original IROC-Z LB9, MT, 22k miles. It sat for a while but got going easy. Here's what I did:
New gas, fuel filter change and seafoam treatment
New tires (they were factory original dry rot!!!!!!)
Fuel pressure + initial timing checks
Charging system check
Oil + filter change
Fluid checks
Drove it hard to make things that had to fail... actually fail. Not that hard but hard enough! Pretty much anything that had rubber it in failed.
Recorded some data stream for diagnostic SES light and stumbling on cold start using laptop and AFR gauge.
Engine bay clean-up
Undercarriage inspection and clean-up
Thorough inspection of about everything!
New air filters
New spark plugs, cap, rotor (wires were good)
New thermostat (was opening too soon)
Reman smog pump... was making a racket
New accessory belt (dry rot)
Thorough coolant flush
Throttle body coolant by-pass (little hose was leaking)
New front brakes (Powerstop Z26) and caliper maintenance
Complete rear brake disassembly + clean-up + lube + new cylinders (were leaking)
New brake fluid and clutch fluid
New braided brake hoses
Manual transmission oil replacement (Dexron III)
Speedometer cable leak fix
New engine rear main seal (leaking)
New clutch throw-out bearing (preventative)
Engine oil pan restoration (rust)
Repack front wheel bearings + new seals
New valve steam seals (was puffing smoke on cold start-up)
New struts/shocks (rear were shot!!!)
New suspension bushings all around (dry rot)
Steering linkage clean up, inspection and lubrification
Alignment
New hood struts
Rear end oil change + posi additive
Oil pressure fuel pump switch by-pass (fuel pump would stay on after shut down)
Reman MAF sensor (was causing issue and SES light)
New battery
Fog light casings restoration (rust)
Complete paint decontamination, inspection, assessment and enhancement. Paint is original.
Fixed a few rattles and T-Top adjustment
Interior was in immaculate condition.
Did not do compression test. It does not burn oil and 1/4 mile times are right on.
Added UMI Performance #2400-B subframe connector to protect chassis integrity. Some light crack had started on driver's B pillar (classic!)
I've been doing fuel filter changes every 500 miles with Seafoam treatment. The brown sediment is getting lesser. I am trying to avoid fuel tank removal and clean-up. I have a set of injectors in stock since it still has the OEM Multec. They have not failed yet!!!!
Did all work myself except welding subframe.
Car runs so much better than when I bought it. These things need a lot of TLC. Next will be A/C restoration. It failed after 1 year...Everything was factory original!!!!
I'm expecting master cylinder and clutch slave/master failure as well as injector failure. Radiator looks good. Water pump and power steering not leaking yet. ICM might fail... and many other things
very tight, I like it. I think i need the answer sheet for the last pic actually.
I'm a little late to the party, but I agree with Tuned Performance. I personally got the 22#hr Bosch D3 injectors on my 305TPI and hated them. Delphi injectors seem to be the way to go in a stock replacement application. I've never heard a bad thing about them. The Bosch D3 injectors are loud, run lean, and have very limited injector information (inconsistent data on the forums as well in regards to their voltage comp. offsets).
I am continuing to diagnose the L98 stock engine for now…My 1991 Service Manual is my new daily reading.
I purchased and installed a new battery.
I think i have vats temporarily satisfied with the correct resistor.
I have disabled the aftermarket alarm i believe.
It now cranks, and security light is gone.
The tach is all over the place.
I have spark.
I don’t think I have fuel.
How do i test the relay on the firewall for the fuel pump? What other fuel related electrical systems do i check and how? There is no sound of the fuel system energizing and it sounds like it will run with starter fluid, it sputters and tries to run but runs out of fuel. I should also mention several it appears several fuses have been removed.
I have purchased all of the pump, sending unit, injectors …however I am attempting to work my way back to the tank in a process of elimination. As well assuming i have a proper output on the fuel relay, is that the last check point prior to the tank is there a way to check the pump is getting power before dropping the tank?
I have purchased a noid light test kit still waiting for delivery. I have not tested for fuel pressure yet as I'm almost certain the fuel pump/relay is not functioning properly.
Thank you for diagnostic advice as I'm still deep in the weeds getting up to speed on this car.
Last edited by Thirdgen4me2; 03-18-2024 at 06:26 PM.
Reason: Added details
Just for starters is the fuse next to the battery there ?
I will check tomorrow. An additional complexity is that im working on it at my storage facility 15 minutes away so everything is a real PITA. And i have no power there so everything is slow and takes lots of planning and prep as far as grabbing tools. I always seem to forget something every time I go.
Here is a schematic of the fuel pump relay, it uses the fuse next to the battery. Prime on green/white for 2 seconds. Power out might be tan/white to pump cavity B.
02-14-2024, 02:22 PM
