Cam Sensor?/Crank Sensor?

[lorries93explore]

I have a 93 Explorer that has been having problems for weeks....Have replaced the fuel pump 3 times, new fuel filter, fuel pressure regulator, and fuel pump relay. It ran ok for a few days then became hard to start and now it seems that the engine and the fuel system don't seem to be communicating. It has left me stranded for days then runs ok for a few miles then starts having trouble again. I have been told that it may be the cam sensor but when I called a parts store they couldn't find that part for my truck. They said that they have a crank sensor.....is this the same thing or something else that may be causing the problems? Thanks for any help.....

 

[MrShorty]

now it seems that the engine and the fuel system don't seem to be communicating.

What exactly do you mean? Does the fuel pump run when it should? If the fuel pump is running, what pressure is it generating? If the fuel pump is not running, the fuel pump circuit is a pretty basic DC circuit and is usually pretty easy to check with a voltmeter and a wiring diagram. I'd probably start by verifying that the fuel system is working.

 

[lorries93explore]

I was getting 30psi, and we can hear the fuel pump come on....the voltage was checked, I don't remember what it was but the mechanic was ok with it. Now along with being difficult to start, once I get going, I seem to be lacking power until I get to 35mph, then I do ok. If I have to stop or slow down a great deal, when I try to accelerate it won't go anywhere runs rough sounds like it is trying to backfire....if I let off the accelerator it calms down, and will start to move, very slowly...until I limp back up to 35mph then does fine until I have to slow down again. Thanks for any suggestions!

 

[MrShorty]

Just to be sure, that pressure was checked when the engine was hard to start and/or lacking power? If so, then it doesn't look like a fuel problem.

Before I started blaming any individual sensor, I'd pull codes to see if the computer will report any problems. It can be done with a paper clip if you follow the instructions in one of the instructional threads in this or the EEC-IV forum

 

[lorries93explore]

I am doing that in the morning...will let you know what I come up with

Thanks!

 

[lorries93explore]

OK....tried the paper clip method to pull the codes....the cel came on but did not flash at all....tried several times...same result. Started the vehicle with the fuel pressure gauge...this time it started first try. Gauge went to 30psi then as we let it run, the fuel pressure gradually went to 20psi. When we tried to rev it up the pressure went to 15psi until I let off the accelerator then went back to 18psi. Any ideas?

 

[MrShorty]

OK....tried the paper clip method to pull the codes....the cel came on but did not flash at all....tried several times...same result.

Sounds like you haven't got it to enter test mode. Usually this is because you haven't made a good connection between STI and the SIG RETurn. Double check all the connections and make sure you are getting good contact. It could also indicate a problem in the wiring between the self-test connector and the PCM or a fault inside the PCM.

However, your fuel pressure numbers suggest to me that the problem is in the fuel system. Published specs suggest the pressure should never fall below 28 psi. Unscientific tests I've done suggest that the engine won't run below 20-25 psi. Assuming the gauge is reading correctly, your fuel system is not running at the correct pressures.

Is the pump running during the low pressure condition? Does it have a stable power supply/ground?
Is fuel being returned to the tank during the low pressure condition? You might be able to test this with a stethoscope by listening to the tank to see if you can hear the fuel returning. Another suggested test is to locate a "soft" section of the return line and pinch it off. If the pressure jumps up (the pump should be capable of generating 80-100 psi), that suggests that the regulator is opening too soon. No change in the pressure suggests that something upstream of the fuel rail is preventing the system from pressuring up (clogged filter or other obstruction, bad pump).

 

[lorries93explore]

Still can't get the cel to give us any kind of codes. We checked all grounds and cleaned some connections. We were staying at 18psi. Once we cleaned the connections, the truck started first try and had 35psi, no hesitations, no problems what so ever. Took it for a test drive...all good. Later, truck started 1st try ran great for 15 miles, was parked...40 minutes later...would start but would not stay started, would die immediately. Now had 20psi. 1 hour later...started first try, stayed started long enough to get it up on the tow truck and sent to the shop. I can't afford a lot of diagnostic charges...any idea what I should have them check first?

 

[MrShorty]

I would probably tell them what you've told us here about your fuel pressure testing and have them dig a little deeper to see if they can determine if the fault is in the fuel pump circuit, the fuel pump itself, or in the regulator.

 

[lorries93explore]

Thank you....I appreciate all your help....hopefully he can get it figured out!