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Losing prime in fuel line........
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Anonymous Poster
mwgrant129@aol.com
Nov 19, 2006, 7:13 AM
Post #1 of 11
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Losing prime in fuel line........
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I have a 1987 chevy blazer 4x4, 305ci engine with fuel enjection. My fuel pump went, replaced with new pump only, not the whole sending unit. Started the truck up and it ran, had a miss so I replaced the plugs, cap, rotor, and wires. Went to start the truck, wouldn't start. If I prime the carb, it'll start up and run fine. If I shut the truck off and try starting it again, won't start til I prime the carb. By working around the carb, could I have disturbed any wires to make it keep losing prime. It only started doing this after the tune-up.
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Anonymous Poster
Nov 19, 2006, 7:28 AM
Post #2 of 11
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Re: Losing prime in fuel line........
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I've checked the fuel lines, there are no leaks that I can see.
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steve01832
Veteran
Nov 19, 2006, 8:04 AM
Post #3 of 11
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Re: Losing prime in fuel line........
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In your first post you said that the truck had fuel injection? Then you said if you prime the carburetor? Is it fuel injected or carburetored? If it has throttle body injection it may look like a carburetor but they are not the same.
Steve
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Anonymous Poster
Nov 19, 2006, 9:16 AM
Post #4 of 11
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Re: Losing prime in fuel line........
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I think it is a throttle body. On top of is throttle body it has 2 things that look like sprayers on each side with wire going to them. I drained the fuel tank to drop it, only put in a max of 5 gals just to start the truck. Could the fuel be to low in the tank?
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steve01832
Veteran
Nov 19, 2006, 2:23 PM
Post #5 of 11
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Re: Losing prime in fuel line........
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If you have 5 gals. in the tank that should be plenty. Let's start with hooking up a fuel pressure guage to the system. I want to check the fuel pressure and then I want to turn the key off but leave the pressure guage hooked up. Check the guage in about 1 hour and let's see if the fuel pressure dropped off.
Yes, this is a throttle body injection system.
Steve
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Anonymous Poster
Nov 19, 2006, 2:55 PM
Post #6 of 11
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Re: Losing prime in fuel line........
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I'm going to pick up a rebuild kit for the fuel pressure regulator. When the fuel pump went, I poured a little gas down the throttle body to see if the truck would start. I had a back-fire and there was a flame in the throttle body. I couldn't get the flame out right away,I may have heated or mealted the rubber diaphragm in the regulator. It can't be that hard to rebuild it, at least I'll know for sure if the regulator was bad or not. If that doesn't work, then we go with the pressure test.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 19, 2006, 3:41 PM
Post #7 of 11
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Re: Losing prime in fuel line........
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Wild stab at this: If you haven't, put in a new fuel filter.
Also: You should hear the fuel pump buzz with just key in run position and shut off when pressure is built up. If not we have to go from there, T
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Anonymous Poster
Nov 19, 2006, 11:54 PM
Post #8 of 11
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Re: Losing prime in fuel line........
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Yes, I replaced the fuel filter but I don't recall the the fuel pump shuting off with just the key on. If the pump doesn't shut off, could it be something in the fuel sending unit, I did leave the old on on. I will double check on that and post back.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 20, 2006, 6:09 AM
Post #9 of 11
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Re: Losing prime in fuel line........
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87 GM 305 (for search ability)
The fuel pump should be able to build up pressure and shut down when more is not needed. While driving this usually can't be heard.
When an engine is started cold the vehicle is supposed to know that and a thing called cold enrichment kicks in like a choke in carbed vehicles. The vehicle gets info on engine temp and makes the call via a sensor which should be near thermostat.
Cheap and worth a try, T
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ucarifix2dy
User
Nov 21, 2006, 4:48 PM
Post #10 of 11
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Re: Losing prime in fuel line........
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need to know how much pressure you have need to know if you have injection pulse and i done this alot make sure your plug wires are in the right firing order it should had not pop when you pure gas down the throttle body
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Anonymous Poster
Nov 22, 2006, 11:44 AM
Post #11 of 11
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Re: Losing prime in fuel line........
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Well, rebuilt the fuel pressure regulator. The metal disc on the diaphram was very badly rusted. Put it back together and it started right up. Thanks for all the help, I learn something new everyday. Thanks again........
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