I have a 2000 Blazer with 70K miles. When the blazer is cold (first time it is started for the day) it starts just fine. It starts as soon as I turn the key over. The trouble comes when I drive it 15 to 30 minutes and it sits for a little. When I get back in and try to start it, I have to hold the key in the start position a lot longet as the engine cranks for a while and eventually starts. I am not a mechanic but when it is cranking it seems like it is not getting fuel. It has a new battery. I replaced the fuel filter (I thought I would try that first since it was an inexpensive first step and it had never been changed) but it is still doing it. It starts just fine when the engine is cold. I only have trouble when the engine is warm. Another thing is that the fuel gauge does not work. It does not go below 1/4 tank and with the blazer in park the needle bounces between E and F. I know this problem is caused by the fuel sensing unit which is part of the fuel pump assembly. Could failure in one part of the fuel pump assemble mean the whole thing is going bad and that is what is causing my starting problem?

 

Let me get back to you on this.
My gut reaction is your fuel pressure regulator is going out. But I want to check something first, unless someone else can confirm this.

 

The only way to diagnose fuel system problems is with a fuel pressure gauge. Even FPR oring leaks can not be diagnosed without a leak down test with a gauge. I've gone so far as to remove the hood of a car/truck and drive it with the gauge zip tied to the windsheild wiper arm for flow problems (fuel pump). Leak down tests should be done from high pressure (full line pressure - ~60psi) and at a lower pressure (~10psi) by purging some of the pressure and watching the pressure drop after that. Some leaks will only show at high pressure leak down and are normally attributed to defects in the oring. Other leaks are due to oring shrinkage or defects in the oring groove/bore and are present only at lower pressures due to the deformation of the oring when under pressure.

 

I'm planning to get a fuel pressure gauge and check the fuel pressure. This is probably a dumb question but are fuel pressure gauges pretty standard. I saw one at Advance Auto Parts and one at Sears (both got apout $40 US) but I didn't know if there was something special I needed to look for to test the pressure on the Blazer. Since I am only having a warm engine hard start problem, if I test the fuel pressure and I don't have 55 to 61 psi does that mean it is the fuel pump. One of the posts mentioned the fuel pressure regulator. The Blazer/S10 Haynes manual only details how to test the fuel pressure regulator on the 2.2L MFI engine. The manual says to have the fuel pressure regulator on all other engines diagnosed by the dealer. Why is this? Thanks for the help.

 

Fuel pressure gauges are pretty standard. Mine came from Advanced Auto and it has worked flawlessly for 5 years.

If you don't have 55-61psi, then you have to do some testing. If you have under 55psi, your truck really shouldn't be starting. A FPR problem will be the same regardless of when the truck was run last and it shouldn't change.

The reason why your Haynes manual doesn't detail the FPR for the 4.3L is because the FPR is under the upper intake plenum and requires a BUNCH of stuff be removed prior to even getting that deep. I've done it and it was not fun, not too bad either, but still don't look forward to getting in there again anytime soon. If I have to, I'll be throwing in the updated MFI spyder from GM that is used on the 04-05 4.3Ls.

 

The reason I asked about the fuel pressure gauge is because the gauge at Advance and Sears (Actron CP7818) states that it is for fuel pressure systems equipped with a Schrader or fuel access valve test port on the fuel line then it list vehicle years through 1996. The unit looks just like the model used in the Haynes manual and the Schrader valve fitting looks like it will fit the valve in the fuel rail of my Blazer but the thing about vehicles throught 1996 made me wonder.

 

Well, my fuel pressure tester came from Advanced and it works fine on my 2000 Bravada, my 2001 Bonneville, my parents 97 STS, and my dads 2004 Chevy Silverado 2500 6.0L. All of which have a schrader valve on them. I did have to use the adapter that came with it to test the fuel pressure on my landlords 1992 Ford E350 moving van.