Help with fuel pump diagnosis

[rlb81]

I tried searching and didn't come up with anything so hopefully someone has a good resource. I was a bit annoyed to open up my service manual to see that Ford has a separate book for Powertrain Control/Emissions Diagnosis.

Anyway, 2002 Explorer 4.0 (non-flex) w/ 155k miles. I've had intermittent no-start problems lately. Sometimes I will turn the key and the engine cranks but does not fire, not even a sputter. Other times it was start, sputter, then die. Trying to start again gives nothing but continuous cranking with no firing. I can get it to fire up by repeatedly turning the key off, then cranking for a few seconds, and repeating until it starts. Its more prone to happen on a cold day and a cold start, but it's happened on a warm start too so the problem isn't so picky anymore.

To me this seemed like a spark problem at first (since the engine would crank away with no indication of combustion) but once the sputtering thing came in to play I'm changing my mind. I've also searched and found similar situations pointing to fuel problems. I'd like to figure out some diagnosis steps before I buy a test gauge, any help would be appreciated!

 

[coolhandguenz61]

I recently had a fuel pump problem with very similar symptoms. Mine is a 2000 V6 OHV so I am sure there is considerable difference however through this site I started the following steps because they were cheap and pretty easy.

1. Remove the MAF sensor and clean it with the appropriate cleaner made by CRC I think at Autozone like $6, look up youtube videos for what to spray, its these 2 little pieces of wire it looks like a staple.

2. Remove the intake manifold and check the throttle body to see if its clogged and super black, then do the same with the IAC (Idle air control) valve and spray it out, again CRC makes an appropriate cleaner.

3. I dont know if its in the same spot but I checked the crankshaft position sensor I believe it is called and sprayed it out with electrical contact cleaner.

4. The next things I checked were the vacuum lines, spark plugs.

I ended up taking it in and my fuel pump was bad (not the entire assembly, just the pump), i didnt know how or have the equipment to do it and it cost me about $550 with diagnosis. There are a bunch of other things it could be i just gave you the cheap ones I started with that a lot of people have had luck with. Start poring over this site theres a lot of other little things people suggest looking at also - Good luck

 

[rlb81]

I'm finally looking further into this. With the cold spell in NJ this week I've been having more and more trouble. Here's what I'm doing in case it might help someone else. This is for a 2002 4.0.

I've determined that the no-start is caused by the fuel pump. I do not hear the pump priming when the ignition turns on. I can usually turn the ignition on/off repeatedly until I hear the pump prime then it will fire up and run great. Sometimes this takes 5-10 seconds, sometimes it takes 2 minutes. I'm trying to determine if it's the pump itself, or another issue.

My gut feeling is the relay is sticky, or the pump has a dead spot. Once the pump fires up it runs great, so I really don't think its a wiring issue (otherwise I'd expect the engine to randomly die). But,who knows......

So far I've checked and re-greased the 2 connectors along the frame rail next to the fuel tank that are part of the fuel pump circuit. I also cleaned and greased the ground that is located on the right D pillar (to the right of the rear cargo stash, behind the trim panel).

I checked the fuel pump relay and noticed it wasn't fully seated, however I don't think that was a problem (it wasn't flopping around in there, and the contacts were still engaged). I am going to replace the relay since it's fairly cheap (~$15).

Next up I will check the connectors on the inertia shut-off switch. I'm also going to hook up a test lead on the output side of the switch to see if there is power in the circuit when the pump doesn't run. I was considering hooking up a lead closer to the pump itself, but I don't want to cut into the wiring that's exposed to the elements. I also don't want to run a hot wire from outside into the cabin. The idea is to be able to check from the driver's seat. This happens a lot when I'm leaving for work in the morning, so crawling around under the truck in office attire isn't ideal.

 

[RicketyExplorer]

Sounds like the fuel pump is on it's way out. It can run for a little bit but just get it replaced and they should also replace the filter too. It set me back $450 + $100 for the tow which was covered by insurance, but the last thing you want is it to die on you on the way to or from work or where ever.

 

[rlb81]

I think you're right, I had the issue again this morning. There's power leaving the shut-off switch so at this point I'm fairly convinced power is getting to the pump and it's the pump that's causing the problem. I'm not sure I can get it replaced for $450 in NJ, though I might just do it myself.

Thankfully I can walk to work if needed and I don't drive it much else otherwise. I might just wait until the weather gets warmer and drop the tank myself. Should be a fun time.