Hard to start when warm, after BHG job

[CyFi6]

Well i fixed my very slightly blown head gasket just last weekend. Ever since, i have noticed that when the car is still hot and i go to turn it back on, after sitting maybe 10-15 minuets, it cranks for a very long time before it starts. Starting in the morning or any other time when the car has cooled it starts rather quickly. Previous to doing the head gasket, the car would start when hot, but would misfire/stumble a few seconds and then clear up, which was supposedly a common issue with pressure being bled off and getting vapor in the rail. When i had the car apart, the only things i did to the fuel system were spray the injector inlet screens out with brake clean, clean the whole exterior of the injectors, and replace the insulators on the front and the o rings on the back, I put some assembly lube on the o rings to make sure there didn't rip when pushing them into the fuel rail. I have no fuel leaks on the exterior anywhere. I just tried to jumper FP and B+ in the diagnostic box under the hood, but when i did so, the fuel pump relay on the opposite side of the engine compartment buzzed like crazy. I did however hear fuel moving, but barely over the buzzing fuel pump relay. This relay does not buzz like this with the car running.

What should i check next? Should i hook up a fuel pressure gauge and check that the pressure holds for 5 minuets like the TSRM states? Thanks for any insight!

 

[Nick M]

A relay buzzing could be weak. I can't say I have heard them buzz before. You sure it wasn't the pump?

Your weak rest pressure is probably even weaker now. You can isolate the check valve in the pump versus the pressure regulator by pinching the return or supply, and having a pressure guage on it. Keep in mind, you can only check one part at a time. But if one is ok, it is likely the other side.

 

[CyFi6]

The relay is definitely buzzing when i jumper the diag. box. It definitely does NOT buzz when the car is running.

So you are saying put a pressure gauge between the pump supply and where you pinch, pinch it, run the pump, then turn off teh pump and make sure pressure holds? And if it doesn't the pump check valve is leaking pressure off. I will try that, i honestly never knew there was a check valve in the pump. Thanks

 

[Nick M]

The relay is definitely buzzing when i jumper the diag. box. It definitely does NOT buzz when the car is running.

I don't think it is suppposed to run constant when the car is not running. It could create a problem.

So you are saying put a pressure gauge between the pump supply and where you pinch, pinch it, run the pump, then turn off teh pump and make sure pressure holds? And if it doesn't the pump check valve is leaking pressure off. I will try that, i honestly never knew there was a check valve in the pump. Thanks

Put the guage on the union bolt. You need a decent fuel injection test kit to find the right pieces. Or you can buy the SST. The gauge on the union bolt goes under the pressure regulator, as you are checking rail pressure.

When you shut the car off, pinch the return. See if it drops. If it drops, it is the regulator side. Confirm it by doing the same thing the next day, or later that day by blocking the return after the regulator.

If it doesn't drop, move the restricter over behind the regulator and see that it does. It has to be one side or the other. Well, it could be injectors, when is the last time you paid for a good injector service? Are you running a premium name brand gasoline, or from the Ma and Pa station. Detergent is added at the refinery, but the big name stations add a little more.

 

[mk3forme]

I hate awakening old threads but rather than start a new one this car is having the same problems as mine. And there was no ending to this one. Hopefully it will help someone else out too. My car starts right up when its cold but have to crank quite a bit when warm. No leaking external out of the motor anywhere but the car smells like straight gas when I get it to start after warm. Im thinking leaky injector. And yes I had all the injectors flow tested and cleaned before reinstalling them. I also have a AFPR. My pressure does leak off after running it but I dont know how long its suppose to stay up after shutting it off. It probably drops to 0 after a couple of minutes.

Question is this. If it is an injector leaking off, how can you test for this or tell which one it is? Thanks in advance for any help.

 

[supraGhost]

my car was also hard to start when it was warm. it turned out to be the spark plug wires believe it or not...


but people suggested to me that perhaps the fuel in my fuel lines was vaporizing from the heat and creating air in the fuel lines and making it hard to start until it cooled down. wasnt my problem but it coudl be yours

 

[mk3forme]

I guess the reason im thinking leaky injector is cause of the gas smells and black smoke after it starts. Only after its warm remember. But the more you crank the more fuel you starting with also. Just wondering for how long my fuel pressure should stay up as well. That lead me to believe it was leaking off as well.

 

[AJ'S 88NA]

If you have a AFPR like an Aeromotive, it says in the info that the pressure will not hold after shutting off.

 

[CRE]

Vapor lock is not terribly common with these cars.

 

[mk3forme]

well I know that fuel pressure is not suppose to bleed off right away. But im not sure how longs its suppose to stay up. Thats why im thinking I have a leaking injector. And if thats that case then that might explain the gas smell as from that black cloud of smoke at startup. I dont remember reading anything on the aeromotive about it not holding FP. Why wouldnt it?