Fuel delivery problem (I think)

[thorney_5]

I recently obtained a 2000 explorer xlt 4.0 SOHC with 149,000 miles. Put new leaf springs, radiator, rear shocks, front axle seals, spark plugs and wires, and changed all fluids (except transmission). New tranny put in at 120,000 miles (5R55E), only thing I thought I had left to do was replace transmission seals. However, after going to start it, it only cranked, and wouldn't start. Started with compression test, checked out ok. Next ignition- distributor tested perfectly, good spark on all cylinders. ( Just to add one thing- engine started while testing spark and everything worked normally for a day or 2, I thought I had solved it, but then went back to the same problem). So now I had it narrowed down to fuel delivery. tried spraying starter fluid in throttle body, and it did not fire. Fuel pressure read 0 psi, and no whine of the fuel pump during priming of fuel system. All relays and fuses check out ok, inertia switch not tripped. Have not yet dropped fuel tank to check wiring there, but it is perfect everywhere else. Also, no trouble codes present. Everything points to fuel pump or ground, but why wouldn't engine fire when given fuel in the form of starter fluid and why would it have started in that 2 day or so period and worked fine? It definitely ran for much longer than it could have on starter fluid alone in that period. My best guess is a bad ground wire at the pump. Is there any way to check this without sropping the tank? If anyone can help your input would be greatly appreciated. Also- love the forum. I read it all the time but decided to join today.

 

[budwich]

Odds are high that you don't have a fuel problem if spraying in starter fluid didn't cause the engine to run at all.

does your check engine light come on with key on, further does it go off during cranking / starter engaged attempts? check / clean the crank sensor.

 

[thorney_5]

Yes the check engine light comes on with key on and goes off during cranking. Checked and cleaned crank sensor, seemed ok. I tried the starting fluid test agin but this time through the brake booster hose and it fired up for a few seconds. Voltage coming out of inertia switch is normal during priming period.

 

[budwich]

check continuity / resistance to the pump. check fuel pressure at rail.

 

[thorney_5]

Whats the easiest way to get to there to test it- dropping the tank or cutting a hole from above?

 

[budwich]

just go to the inertia switch and test there.

 

[thorney_5]

Isolated problem to past inertia switch. Voltage good coming out of switch. 99% sure its wiring at the pump or the pump itself.

 

[budwich]

I didn't ask about voltage... I suggested continuity and resistance measurements. That's how you check wiring and the motor.

 

[thorney_5]

What 2 points should I test resistance between? Relay and inertia switch? Resistance within the switch itself? I'm not the greatest with electrical things....

 

[budwich]

You unplug the wire from the pump going to the inertia switch and measure the resistance going to the pump (to ground). You already said you have voltage at the inertia switch (assuming 12v)... that tells you the wiring (from relay to the switch) to there is good.... now you are trying find out if the wiring going to the pump and and the pump itself is electrically connected in "some form".

 

[thorney_5]

Since I was going to have to get to the pump anyway, I cut an access panel and pulled the pump. I bench tested it and it wouldn't run. reversed the polarity, and it spun perfectly. Back to normal polarity , wouldnt turn. Kept going back and forth until finally it worked in the right direction. Ran it for around 5 minutes then reinstalled in truck. This was yesterday morning, and the pump worked great ever since. I think I'm still going to replace it so I don't end up stranded on the road somewhere. Found a new pump for $40 so I ordered a spare as well.

 

[2000StreetRod]

running pump dry

Fuel pumps use fuel for cooling. I advise against running your new pump without fuel to cool it or it may be damaged.