I have a 2001 blazer LS model 2wd 4.3L. For the past week, it doesnt want to crank in the morning or after it has sat all day while I am at work. We were thinking it was the fuel pump, the fuel pump is just now 3 yrs old, so my husband tested the PSI and it is 58 when you crank it, then after it sits it only drops down to 55, so we concluded it is not losing prime. Does anyone have any other suggestions?

My husband thinks it could be the fuel filter, but I am doubtful because it drives fine, the time there is a problem is when you crank it up after it has sat.

 

What do you do to get it to start?

 

turn the key off then turn it back on and it cranks right up.

 

Try the leak down test one more time without cranking it. Just put the gage back on turn it to the key on position bleed off the gage. Then cycle the key again. It needs to be in the off position for at least five seconds for the prime relay to work again. If you still hold at least 55 after ten minutes you should be good on the pump and injector end.
After that I would go to the Blazer Forum homepage and in the Google box type in "ignition switch" and see if anything you read seems to apply.

 

To do a proper fuel pressure leak down test you need to measure the fuel pressure with the key on, engine off. The fuel pressure should be between 60-66psi, and should remain above 55 psi for at least 10 minutes after you turn the key off. It's also a good idea to test the fuel pressure after the truck has been sitting for a few hours so everything is cold, just like the situations where it isn't starting.

If the truck doesn't start the first time you prime it, and you have to turn the key off, and then back on to get it to start sounds to me like your truck is not reaching proper fuel pressure to start correctly. The fuel pumps can be sensitive to good battery voltage, especially as the pump gets older. Remember that as the truck is trying to crank the engine the battery voltage will drop quite a bit, and that will reduce the fuel pump's power when trying to start the truck.

All that being said, there are several other components in the fuel delivery system that could be causing the problem, like the fuel pressure regulator or stuck poppet valves. Hopefully Captain Hook will chime in on your problem. He's an ace at trouble shooting.

 

Ok one of the guys I work with said it could be my ignition coil. My brother n law said that it is a little loose. Would that cause this? I put a fuel cleaner in it just to try.

 

You're on the right track! 58psi is too low and it will cause long cranking times or not start at all, especially after it sits awhile.

On your 2001, in the underhood fuse panel there is a vacant terminal next to the fuel pump relay. With the ignition OFF, and the pressure tester connected, install a jumper wire from battery positive to the fuel pump prime terminal. The fuel pump will run continuously with the jumper wire in place. After the fuel pressure stabilizes on the tester, note the pressure, it must be 60psi to 66psi. Next, remove the jumper wire. Wait 10 minutes and note pressure reading. It must remain above 55psi. Post the results for both parts of the test. If it passes both tests, the fuel delivery system is fine. If it fails one or both parts, there is a problem with the fuel delivery system, and will require further diagnosis to pinpoint the problem.

 

Sorry, just getting back to this. I borrowed the tester from a guy at work and had to give it back so I can't test the pressure with the jumper wire. Now it doesn't want to start at all. The fuel pump is kicking on still. We tried to have the codes ran but it won't link up to the scanner at either parts store. Not sure if it's the port or a fuse. My husband bought the fuel pump but I don't want him to put that in until all other options are exhausted.

 

We really need to know what the fuel pressure and leakdown rate is, ain't no two ways about it that's the first step. Most auto parts stores rent/loan pressure testers, for free. If you choose to buy one, (not a bad idea when you own a Blazer) they are ~$40.

 

Do we have to wait and let it sit before we test the pressure again?