fuel pump issue- would you agree?

[Jay87LX]

1999 expy 5.4, just turned 130K. several times in the last few days the truck has just stalled. Pull to the side of the road, crank it over and sometimes it will start right back up sometimes it takes several minutes.
Its not electrical.
I am thinking fuel pump issue- thoughts?

 

[stamp11127]

Check fuel pressure before condemning the pump.

 

[Jay87LX]

do I have to wait until the truck dies and then see if I am getting pressure or would it show weak pressure while the truck is running if the pump is on its way out- what pressure should I be looking for?

 

[Dizzy]

When running the air or under load, does it drop hard into second gear? The stalling and what I just explained happened to me until I replaced the fuel filter. Never had problems again. But, it was on 5.4 F150. Same thing really.

Diz

 

[Jay87LX]

When running the air or under load, does it drop hard into second gear? The stalling and what I just explained happened to me until I replaced the fuel filter. Never had problems again. But, it was on 5.4 F150. Same thing really.

Diz

the last 2 times it happened is when I released my foot off the gas, like approaching a stop sign, had less than a quarter tank of fuel and had both front and rear ac on high

 

[Dizzy]

it may just be starving for fuel. outside of a pressure check, changing out the fuel filter is an easy check.

Dizzy

 

[toms89]

You may try cleaning the IAC valve. Heavier load with closed throttle puts different demands on it (more airflow required). It also controls minimum airflow for start up. Would check the throttle body as well for build up around the throttle plate when she is shut.

 

[toms89]

IMO.. The problem as you describe it makes me believe it is airflow not a fuel issue.

 

[docraymund]

If you could have the fuel pressure checked first it would be better otherwise if you don"t have access to that service it would be best if you have the fuel pump and fuel filter replaced now. You don't need the whole assembly, just the pump. You don't want to be stranded in the middle of nowhere eventually.

 

[Jay87LX]

I do know I need an IAC. I have had it before where I would start it up and it would immediately die, wouldn't idle. I would go under the hood and whack the IAC a few times and all was good

 

[Jay87LX]

we have a car lot and my mechanic I am sure has a fuel pressure gauge- what pressure range should I be looking for"?

 

[Jay87LX]

So today I changed the fuel filter, cleaned the TB and replaced the IAC,
Drove all the way home 15 miles, no issues. Pulled up to the mailboxes, got out and left it running, It shut off a few seconds later and took a few tries at cranking before it started back up. Back to square one-
I know I have to check the fuel pressure but what is the acceptable reading?

 

[stamp11127]

I think it is 35-40 psi engine running. You also want to see if it bleeds down with engine off.

 

[Jay87LX]

I just did some googling and came across a similar issue and they resolved it with a relay PN It is the fuse relay. At Ford Dealership, the item is listed part # F5TZ*14N089*B RELAY LIST PRICE $16.24.


Here is their reply
"This relay has been replaced twice in our 2003 Ford Expedition. We were on the interstate when our vehicle shut down completely and had hard time maneuvering it. Vehicle would turn on and off. Always keep one in stock in vehicle. "


I am thinking it could be a possibility, as was said it happens when I have all the loads on like headlights, fogs, radio, front and rear AC and also it is very hot outside
It could be a possibiliyty that the relay is heating up, then stoping fuel flow and then it cools down and become operable??? The only thing that stops it seems is fuel flow, once the truck dies all the fans are still blowing strong etc so its only affecting fuel flow

 

[stamp11127]

My past experiences with relays are they weld the contacts together or the coil fails. It is possible that the relay is failing though. I would still see what the fuel pressure is first.
You can bypass the relay with a jumper to test. Just remember to unplug it when you stop.

 

[Jay87LX]

I am going to check the fuel pressure for sure but one thing that leads me away from that is that until it dies I am have no driveability/runability issues. Like when I was parked at the mailboxes it was idling normall and then just shut off in an instant. I would think if I was losing fuel pressure it would start to idle funny before dying- Just my thoughts

 

[stamp11127]

Those symptoms are also for a failing fuel pump. When they overheat they may take out the connections at the pump. You only find out after you remove the fuel pump assembly and inspect.

Since yours is a 99 the pump may be original. I bought a 99 mechanic special that had a failed pump @179,000 miles. I usually only run them to 150,000 miles then swap them. From a maintenance stand point it wouldn't hurt to change yours and the relay.

 

[Jay87LX]

That was my next step- but such a PITA job- I did see once at a junkyard they pulled the carpet and cut a hole in the floor to access the pump- LOL

 

[stamp11127]

It isn't that bad as long as the tank is near empty. Just get it high enough in the air to work underneath. I could have gone up a few more inches but still managed to get it swapped out. I just barely fit at the pumpkin.

Biggest pain was two lines that didn't want to release. Once those finely released it was a piece of cake. Air tools or portable impacts help a bunch and really make a quick job of it.

 

[Jay87LX]

I just went on Rockauto to order a pump and they range from $21 and up to $100.
Anyone have any suggestions, I don't want to do the job twice, but don't want to waste any money if the lesser priced pumps are just as good.
Also some of the pumps are asking "wide or thin electrical connectors"
Anyone know which one would be in my 99 with 5.4 4WD?