2000 4.0 Explorer, sometimes won't start.

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Oct 28, 2013 | 01:45 PM

Khannink

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2000 4.0 Explorer, sometimes won't start.

Hey. I have a 2000 4.0 Explorer that sometimes will not start. It has happened on cool mornings as well as hot days after I shut it off, for example, shutting it off to fuel up. I always turn the key to the on position and wait a second or two before cranking, and when I do that, I can usually hear the fuel pump. It's when I don't hear the fuel pump that I know it won't start, and sure enough, crank and no start. My question is, is the fuel pump going out? Or another thought I had was maybe the inertia switch starting to fail? Any help is appreciated. It runs great when it starts, just has a problem starting sometimes.

Oct 28, 2013 | 07:35 PM

shorod

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From: Cedar Rapids, IA

To determine better whether the issue is with a lack of voltage to the fuel pump or the pump itself, you'll need to check for voltage at the inertia switch (easy) or fuel pump (more difficult, but more accurate) when the fuel pump fails to run. If you don't have voltage, then the issue is something more than the fuel pump. If you have voltage at the inertia switch, then the issue may be with the wiring or may be an issue with the pump.

-Rod

Oct 28, 2013 | 10:43 PM

Mikeman

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Joined: Apr 2000

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From: PNW

Adding to what shorod said, here are some other things you can try without busting out the DMM. Motors can get a bad spot on them and not want to start. The next time the fuel pump doesn't come on, whack the bottom of the fuel tank and see if the fuel pump starts. A little jolt will get the motor off the bad spot if there is one. I use this when a starter won't turn over at all and I know the battery is good. Quick and simple.

You could also try this with the fuel pump relay. Give it a light tap to see if the relay is sticky. Even if it's not sticky, it could still have worn contacts. If there's another relay of the same type in your relay panel, try swapping.

Nov 26, 2013 | 12:08 PM

ztzozm

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From: Coastal Carolina

The fuel pump relay (FPR) on a 2000 is on the pump. The old rubber hammer to the tank could jar it as well as overcome a flat or dead spot on the DC motor pump in the tank.

Nov 26, 2013 | 02:43 PM

Khannink

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I tried swapping relays underneath the hood, still same problem. I did not know that the FPR was on the pump itself, good to know. I will try tapping the fuel tank next time it won't start, which will almost assuredly be today. Sometimes when i try to start it, it will run real rough, barely running, and the tach says it's at about 2 or 3 hundred RPMs. When that happens I just turn the ignition off and try again. Could that be caused by low fuel pressure? Still no check engine light either, which makes it a little harder to diagnose. What should I check next?

Nov 26, 2013 | 04:48 PM

ztzozm

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From: Coastal Carolina

Quote:

Originally Posted by Khannink

I have a the same problem, at least an intermittent problem, however, I have replaced the relay and also coated with Stabilent 22 for good measure. It seems to occur in colder weather. I put a fuel pressure gauge on the fuel rail and watched. Ignition on the first time out, I got only 20#, I did not try to start it. Then with a cycle off then on again, got to 60#. Off and on again several times, got to 60# and, of course, it started. Also, the pump buzz was clear when I got to pressure on the rail. I suspect the ignition switch, any feed back on that? I can't wait to bang the fuel tank, but the last time all it took was one or two cycling of the ignition switch from off to on.

Nov 26, 2013 | 08:49 PM

FireMe

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Joined: Nov 2008

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From: Northfield, MI

Quote:

Originally Posted by Khannink

Still no check engine light either, which makes it a little harder to diagnose.

Fuel pump circuit codes don't turn on the check engine light. Actually there are many, many codes that don't turn on the check engine light. Only codes that effect emissions are required to turn the light on. So, checking for codes may give clues of whether or not this is caused by a fuel pump circuit fault after all.