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-   -   Definitely have fuel problem. Not the pump (https://blazerforum.com/forum/performance-brainstorming-38/definitely-have-fuel-problem-not-pump-35109/)

cage47 09-25-2009 08:43 PM

Definitely have fuel problem. Not the pump
 
OK so I've found that I have a definite fuel problem. I've already replaced the pump and I know that's not the prob. Today when I went to takeoff from a stop it stalled and it wouldn't start right off. I sat in the middle of the intersection trying to start it until it finally turned over. Also lately starting has been rough in general. First thing in the morn it will start but only seems to fire on a few cylinders and eventually gets up to all cylinders in a minute or two. But today I stopped at the mall. After a little time walking around went back out and no start. Took the opportunity to pull the cap off and check the pressure at the spicket on the fuel line. NOTHING! Now granted it was down just under a quarter tank but it should have had enough. Well I got two gallons and got it to start finally. But when I got it home I noticed that the connections to the fuel pump relay in the dash were kinda loose. After finally getting to it I pulled the wires out and bent the connections back into place. After that it starts right up now. No missed cylinders. But that wouldn't explain the stall.

I've done some checking on my own. The fuel pump relay only runs the fuel pump for starts. As is known it only turns the pump on for three seconds to prime the fuel. But I found that if you pull that relay after the truck is running it KEEPS RUNNING. I've gone over the wiring diagrams and it shows that there is an oil pressure/fuel pump relay that supplies the charge to the fuel pump during regular driving. And I confirmed this with my volt meter. That when the truck is running, there is no power to the fuel pump relay solinoid. Not the wire that goes to the pump but the wire that activates the switch. That is the circuit that is only activated for 3 seconds. Again I verified this with my volt meter. So it is the circuit from the oil pressure/fuel pump relay that supplies the charge to the pump during regular driving.

This is my next thing to find and fix. I've done some searches on here and some people don't even believe this is an issue. I can verify, yes it is. My only question is WHERE THE HECK IS THAT DAMNABLE OIL PRESSURE/FUEL PUMP RELAY???!!!! I'm checking all through my haynes manual and can't find a location for the 95. A 96 it shows at the back of the engine, but in the 95 that is actually where the fuel lines are. There is nothing else in the way. Gonna do some more checks. And I'll keep y'all updated. But if there has been another in-depth write up on this on here point me to the thread as I couldn't find it doing a search.

cage47 09-25-2009 10:02 PM

I've found a diagram that shows the oil pressure switch on the back of the engine by the distributor. Problem is on my engine it's not there. That is where the fuel lines come in. Am I missing something?

We got home tonight at 5:30 and at 10 I went out and turned it over. Fired right over first try. And no loping like before. Will try again tomorrow morning.

reelbroke2 09-25-2009 10:29 PM

true,,the fuel pump is also tied into the oil pressure sending unit which is located at the rear of the engine driver side by the distributor..fun to get to.

cage47 09-25-2009 10:37 PM

You have a 95. It is definitely back there? Reason I'm asking is I had an issue in the spring. The radiator fan broke off and sliced the radiator. It was really cold out (-5 with a wind chill of -15). When it sliced the radiator I had to drive another two miles down the road to an advanced auto to get a new radiator. (Yeah, had to replace the radiator in that miserable cold! Took me only 15 minute though in the advance auto parking lot, did I mention it was WINDY!) Anyway. It didnt' damage the engine perse. I've done compression tests and all cylinders are good. No head leaks. No antifreeze leaks. But I'm wondering if the heat might have (or just age possibly) worn or damaged that sending unit. I was considering maybe the spider unit might be getting bad. But that was until I saw that when this happens I have NO FUEL at the spicket on the fuel line just behind the plenum.

So again, as I have the issue with the fuel pump relay in the glove box fixed this is the last thing I need to check. Now if it doesn't stall after this I might have it fixed, but that relay doesn't control regular fuel pressure. That's why I think the oil pressure sender is bad. any hints as to HOW THE HECK TO GET TO IT? (please don't say take the distributor out, PLEASE!)

reelbroke2 09-25-2009 11:22 PM

its easier to get to if you remove the upper plenum, but you dont have to..its next to the distributor unhook the wires and it unscrews,,,its a pain to get to but can be done...

cage47 09-26-2009 11:08 AM

HOW the heck do you get to that thing? Even with the plenum off. I think I can see it. but heck. There's no clearance with the distributor in the way to even get your hand back in there.

On the side it seems to be starting good now. No problems like before. I'm hoping that fixing the fuel pump relay connections fixed it.


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