Up To 10 Seconds to Start Normal?

[Black Red '90]

First post….

I recently purchased a 1990 ZR-1. I understand the LT5’s take a few seconds to start, so I shouldn’t expect anything instant. However, I think mine might be taking a bit too long. It cranks for 4-5 seconds when cold and double that when warm. When I purchased the car I knew secondary injectors were shot as it stumbled bad in full power mode. That was task #1 which I thought may help with the slow start. I installed a set of FIC injectors and replaced the fuel filter. The car ran like a champ afterwards, but it still started slow. I then replaced the spark plugs with NGK BKR5EIX-11 (the old ones looked fine). They made no difference with the slow start either. The 700 CCA battery is less than a year old and doesn’t strain when cranking. The car has 6,500 miles. Any other suggestions?

[TX '90 ZR1]

Congratulations on your purchase.
I recently went through a situation similiar to what you are describing.
Mine seemed like it was taking longer than normal to start. Discovered that the fuel system was not holding pressure after shut down.
After repairing it mine starts just like it should.
Might try this. It's simple to do, so might as well give it a shot.
By the way, did you change all 16 injectors or just the secondaries?

[Black Red '90]

Thank You
I replaced all 16 injectors. What issue did you find with the fuel pressure?

[TX '90 ZR1]

Originally Posted by Black Red '90

Thank You
I replaced all 16 injectors. What issue did you find with the fuel pressure?

I chased it all over the place.
The common places for pressure leakage are the injectors, fuel pressure regulator and fuel pump check valves.
I did not really think it was injectors as mine are only a couple of years old.
What I did was disconnect the fuel outlet hose on the fuel tank sending/pump unit. I applied pressure into the hose going to the front of car. (Be careful not to apply over 50-55lbs. I used 45 initially) The system held the pressure so this eliminated the injectors, pressure regulator and any connections in that direction.
Next I applied pressure into the tube on sender/fuel pump unit. Pressure did not hold. I suspected fuel pump relief valve so changed both pumps as I did not know the age of the pumps and had a new set on the shelf. This did not correct the problem and both removed pumps checked OK.
Pulled the unit out again and used soapy water in a spray bottle to check for leakage while applying pressure. Discovered the "Y" fitting that the hoses connect to had a small crack at one of the seams.
I did a temporary repair and replaced all the hoses as they were very hard. (I think everything in the unit was original). This stopped the leakage.
Car starts quicker and just overall acts better.
I plan to come up with something to replace the "Y" fitting for a permanent fix. Just have not decided exactly which way to go yet.
To do the pressure tests I have a tire inflator with a guage and relief valve that I modified to use in situations like this.
There is a procedure in the FSM that describes checking fuel pressure issues, but I find using my procedure is easier, especially if working alone.
Full disclosure, I gathered the idea for testing like this from posts in this forum.
Good Luck!

[Paul Workman]

Congratz on the Z, and welcome to the BEAST!

Sounds like your in good hands - nuttin' else to offer just now, 'cept to say maybe the only thing worse than a lot of hard, neglected miles is NO miles at all!

I'd want to change clutch and PS fluid and flush the cooling system and replace the coolant with the old GREEN (glycol) antifreeze.

Are the tires more than 6 years old? If so, put some new rubber on the list (mine 90 had the original rubber when I bought it in '07 and were like plastic!).

Those square-tooth gears in the early ZR-1s will whine and growl a little...which is normal. With new plugs and injectors, it should idle OK, but know that if for any reason the idle should be less than perfect, the dual mass FW halves will knock a little - sound like a rod knock (cases exists where the engine was miss diagnosed by a mechanic and subsequently pulled the motor to tear it down, only to find "no change" when reinstalling the motor!).

Anywayz.... You've come to the right place for anything ZR-1 related. Welcome!

[Black Red '90]

Originally Posted by Paul Workman

Congratz on the Z, and welcome to the BEAST!

Sounds like your in good hands - nuttin' else to offer just now, 'cept to say maybe the only thing worse than a lot of hard, neglected miles is NO miles at all!

I'd want to change clutch and PS fluid and flush the cooling system and replace the coolant with the old GREEN (glycol) antifreeze.

Are the tires more than 6 years old? If so, put some new rubber on the list (mine 90 had the original rubber when I bought it in '07 and were like plastic!).

Those square-tooth gears in the early ZR-1s will whine and growl a little...which is normal. With new plugs and injectors, it should idle OK, but know that if for any reason the idle should be less than perfect, the dual mass FW halves will knock a little - sound like a rod knock (cases exists where the engine was miss diagnosed by a mechanic and subsequently pulled the motor to tear it down, only to find "no change" when reinstalling the motor!).

Anywayz.... You've come to the right place for anything ZR-1 related. Welcome!

Tires are date coded 1917 so they are in good shape. I've already changed the brake fluid, coolant, serpentine belt, and oil. Haven't done the p/s, trans, or diff fluids. The idle is smooth.

Thank you for the welcome!

[Bob Eyres]

Here's a cheap fix that might work. My 91' had a slow start condition like you described, but otherwise ran ok.
Then one of my fuel pumps failed, and after replacement, ($100 pair-RockAuto), the slow start condition went away. It now starts instantly.

It may not be your problem, but I would bet it is. Even if not, it's an easy place to start. And take a close look at those hoses too.

Good Luck

[Black Red '90]

Just had a car out for a quick drive. I stopped to take pic and the car fired back up instantly (quickest its ever started) after only being off for 30 seconds. I definitely think its fuel related. Something is loosing pressure when sitting for a while. I'll looking into the fuel pumps and lines. Thanks for the input.

[We Gone]

Grats, Your good the LT5 has to find #1 every time before it starts.