Hi: I have a 2000 Blazer with a perplexing starting problem - No error codes. Most times it starts immediately and runs very well. No missing, no idling problems etc. Occasionally it will grind for a minute before catching - usually after sitting for a day or two. Other times it will start and kill immediately, and then start normally on on the next try. It may run perfectly for a week or two before renewing the problem.

I have considered the EGR valve and Fuel Injector system, but no misses when running and lots of power.

I have new plugs, distributor cap/rotor, and fuel pump. Fuel pressure primes to 60 PSI and 65 PSI when running - 50 PSI after 30 minute shutdown.

I nave search threads but can't find any problem quite like this.

 

Key ON, engine OFF, with the fuel pump running, 60psi is borderline low. GM does not publish any engine running fuel pressure specs as there are far too many variables involved. However, 65psi with the engine running indicates a problem exists. This link explains how to do the tests necessary to locate the problem: https://blazerforum.com/forum/2nd-ge...eakdown-88305/ Post all 4 readings and we can analyze them for you.

 

I finally managed to get all the parts necessary for a complete fuel pump/regulator test. I used a gauge purchased at Autozone a while back.

Maximum pressure at filter after activating pump - - 98 PSI
Leakdown after 30 minutes - - 65 PSI

Maximum pressure at engine outlet after cycling pump - - 61 PSI
Leakdown after 30 minutes - - 59 PSI

PSI with engine running - - 65 PSI

I am still at a loss as to what is the actual cause of the intermittent starting problem.

Is the regulator going bad?

I don't think the fuel pump is the problem.

 

There's a problem with the numbers. My guess is that the pump was not running when you took the readings. The clue here was that engine running pressure showed higher than regulated pressure, which should never happen.


Use the pump prime terminal in the underhood fuse panel to activate the fuel pump for testing.
The ignition must be in the OFF position for all tests.


The fuel pump MUST be running when you take the readings.

 

Thanks Captain, you are correct. I was using the key and assumed that since the prime didn't go over 61 when was running that it would make no difference. I redid the test using the fuse panel terminal and it increased to 65 PSI.

With no error codes showing what do I check next.?

 

65psi with the pump running is fine. That is your regulated fuel pressure, it should be 60-66). What was the pressure 10 minutes after you removed the jumper wire?


When you checked pressure and leakdown at the fuel filter, did you use the terminal in the fuse panel? If not, you might want to test it again

 

I was finally able to pinpoint the actual problem in starting. I attached the fuel pressure gauge on the engine and left it there for almost a week. When the next starting problem happened I immediately open the hood and saw that the pressure was 45 PSI and falling, which should never happen. The fuel pump was apparently dumping the pressure it was creating. Bad Fuel Pump.