 not getting enough fuel pressure. Whats up?, Fuel pump?? |
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| RFoulds |
 Dec 8 2010, 04:06 PM
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#1
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914Rennsport  Group: Members Posts: 858 Joined: 10-August 09 From: La Quinta, CA Member No.: 10,656 Region Association: Southwest Region 
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having an issue with fuel pressure. Fuel flows freely from the end of the tunnel lines, connecting to fuel pump. (its a 74 1.8 with stock FI)
fuel pump has been thoroughly checked out and seems to be good. But, fuel pressure is not enough to get a squirt out of the injectors. Instead, while cranking, the fuel is barely dripping out instead of a good spurt. all fuel lines are new, injector rails are good, injectors all good. Any ideas what is causing this?? |
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| r_towle |
Dec 8 2010, 04:15 PM
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Custom Member Group: Members Posts: 24,705 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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The pump shoots it out at something like 60PSI.
The regulator (which is a rising rate regulator on Ljet) reduces it to ~30 PSI) Bernoulis principle keeps the whole system, the whole loop at the same pressure based upon what the regulator is set at...its a physics thing...but its true none the less. Put a real fuel gauge (a test gauge) inline both before and then after the regulator to see what is happening. The regulator is on the drivers side inline just beofre the injectors in the fuel route/fuel lines and its bolted to the head tin near the rear of the engine bay. It could just be a dying regulator...might be time for replacement. They are adjustable if you turn the bolt, but you need a gauge setup after the regulator (between the regulator and the fuel pump on the return line) to know what you are setting it to. If you want to figure out the plumbing...there are two little bolts in the metal fuel rail that are specifically for hooking up a fuel pressure gauge...I have yet to find, or bother to find, the plumbing to get my gauge plumbed into that little itty bitty hole....but its there for this test. I have a fuel pressure gauge with two 3 inch hoses on it, and two barbed fittings on the ends of those...I can slip it inline on most any car pretty quick.. Standard FLAPS diagnostic tool if you go down that isle. Rich |
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| sfrenck |
Dec 8 2010, 04:21 PM
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#3
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Member Group: Members Posts: 492 Joined: 28-February 10 From: Wilmington, DE Member No.: 11,411 Region Association: MidAtlantic Region
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Had similar issues a while back
Everything Rich just said + -Check the fuel filter. Old/dirty or backwards (ask me how I know that one) can cause a large pressure drop on the system. -Make sure your pump is piped correctly Scott |
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| pcar916 |
Dec 8 2010, 04:37 PM
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#4
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Is that a Lola? Group: Members Posts: 1,523 Joined: 2-June 05 From: Little Rock, AR Member No.: 4,188 Region Association: None
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If you block the return line and your fuel pressure goes up beyond normal the regulator is bad. But only do it for a moment or two.
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| ConeDodger |
Dec 8 2010, 04:55 PM
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#5
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Apex killer! Group: Members Posts: 24,097 Joined: 31-December 04 From: Tahoe Area Member No.: 3,380 Region Association: Northern California
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Ground? On the '75 the fuel pump has its own ground, under the fuel tank just under the driver side of the tank...
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