1991 ZR1 Restore - Help!

[kapkanimd]

Hi everyone,

I picked up a non-running (had known bad fuel pumps) '91 ZR1 with 56k miles on it as a project to restore.

Here is what I have done so far:
- 2 new Suburban Fuel pumps & fuel filter
- new fuel pressure regulator & injectors
- all new coils, spark plugs, & wires
- new belt and belt tensioner

- rebuilt damaged vacuum system (tested now working)
- cleaned up plenum, injector housing, throttle body, starter, etc. & replaced gaskets
- new calipers, brake hoses all around, & brake fluid (rotors were turned)
- flushed clutch fluid (no pressure when I got it)
- new K&N air filter
- replaced oil & filter, trans oil, and differential oil
- new battery

After finishing, the car cranked right up on first try. It ran rough, and would cut off randomly but would restart right away. After a few minutes, everything smoothed out and it would idle perfectly up to temperature. I did notice that the vacuum pump would now start running constantly (which was frustrating) so I new something was now leaking, but it still ran.

The next day, I started it up, ran/idled perfectly up to temperature. A few hours later, went to start it, and now it is just cranking but will not start/run! I lifted up the plenum, found & fixed the vacuum leak, and sealed it back up. Still no start!

I checked fuel pump fuses, jumped the fuel pump to hear it run, and used my MT2500 - everything checked out as normal. Next step is get a fuel pressure gauge, but not sure why fuel would all the sudden be an issue.

Any other thoughts? Things I should check? If I need to I can pull a plug to check for spark, but working on it alone and will have to wait for help.

Thank you in advance!!

[viper107]

91 cars were horrible for ecm,s going bad,they had a updated version I think they were putting in 94 ones,are the injectors new or rebuilt

[kapkanimd]

Originally Posted by viper107

91 cars were horrible for ecm,s going bad,they had a updated version I think they were putting in 94 ones,are the injectors new or rebuilt

Brand new accel injectors.

Any way to test the ecu or determine if it?s bad? Any Tampa area ZR1 owners I can swap ecu's with to test if that's my problem?

This car also came with a Doug Rippie Motorsports chip. I just swapped it out back to the factory chip, and it didn't change anything...

[viper107]

Does it have and ecm codes? If it has alot of wierd codes or it says loss of communication it's probably the ecm

[kapkanimd]

Originally Posted by viper107

Does it have and ecm codes? If it has alot of wierd codes or it says loss of communication it's probably the ecm

No codes at all.. when it was running no check engine light and when I ran It through the MT2500 there were no faults and everything tested fine

[viper107]

You Shure you don't have the fire order off?

[viper107]

Does it sound like it has compression? Do a compression test,fuel pressure test,and spark test

[richarde]

Has the fuel quality been checked? Could water / bad fuel be the source of the problem? My black '90 had been left outside for 8 years before I purchased it - Both fuel pumps were rusty / inoperative which I replaced along with the fuel filter and fresh fuel. I also checked both the fuel input and return lines - both contained lots of horrible sediment that would have passed straight through to the fuel rail, regulator and injectors.

[kapkanimd]

I swapped the wires one at a time so am 99.9% sure the order is correct. I will start with the fuel pressure and spark tests. The fuel tank was completely emptied and cleaned then 5 gallons of fresh premium put in. I did not specifically blow out the lines but hopefully that wouldn?t be enough to kill the New injectors.

I did notice the tach was quite off which I initially contributed to the gauge cluster common problem. However when I displayed the rpm on the HVAC screen it was matching what the tach displayed (which was going up to 9k rpm though you could clearly tell the engine wasn?t that high). I read another post on here about a non start due to failed crank sensor.. so now I?m thinking i should test/replace it.

[Z51JEFF]

Here's a long shot,check the airbag fuse. If the fuse is removed,blown the car won't start. Regardless of what it is based on your mechanical skills you will find the issue.