Hey guys - I just picked up a 94 F150 4.9 yesterday. Ran great on the drive home. Took it for a spin after dinner and it started acting up once the truck got hot.

once I open the hood for 10-15 minutes, I can drive for another few minutes.

I ended up replacing the ignition module in the fender well as well as the IAC already. No change.

Ill be stopping for a fuel pressure gauge on my way home to see if I’ve got a pump on the fritz. Only thing that makes me believe it may not be the pump, is that it acts up on either tank.

Any input is appreciated.

 

Check this part. Not sure it is your problem but???

Fuel Injection Technical Library » Engine Coolant Temperature Sensor (ECT)

 

This is an interesting issue, and one that we have had....... It might be the following:
We had the fuel pump go out on Marsha, and replaced it 4 times........ In less than a year.....
The 6 CYL fuel pump is not the same as the 8 cyl fuel pump.
The issue is that someone replaced the fuel pump with the fuel pump for the v-8 model.
The 6 cylinder model due to the location of the fuel piping runs really hot compared to the v8 model.
If the 6 cyl fuel pump goes out, everyone thinks the v8 will work fine, however the 6 cyl fuel pump works at a higher pressure to prevent vapor lock in the fuel piping a the rear of the engine. The v8 pump goes to I think 42psi, and the 6cyl pump starts at 42 and goes to something insane like 60 psi. So the Ford engineers bumped the pressure up with a higher pressure fuel pump to prevent this on the 6 cyl engines)
The wrong pump in the truck acts exactly as you are describing.
Easy test, there are two, One the Codes with throw something weird like the left side cylinders are not firing correctly,
The second test. There is a sharader cap and valve on the fuel piping that you can hook a gauge to and measure the fuel pump pressure. Make sure you measure at higher engine rpm not just idle.

The only solution is to get the OEM real Motorsport Ford fuel pump for the 6 CYL..... There are no after market pumps that will work right with the 6 cyl that we could find...
I looked into trying to get a rail mount fuel pump set up, but there were a lot of considerations that I didn't feel like solving....
G

 

A wonky TPS can display those symptoms as well. Not difficult to change on the 4.9L.

 

before buying more parts, check for codes, even if the CEL(Check Engine Light) isnt on, could be stored codes
Fuel Injection Technical Library » How To Run a Self-Test



And on buying your ICM=TFI make sure it is one listed in pic below, parts stores dont know that Ford changed them from push-to-start, to CCD


pic courtesy of rla2005

 

Yes it is. Same pump for all gas engine trucks.


See response above.


The fuel pressure regulator determines the fuel pressure at the rail. Yes there is a specific regulator for 6 cylinder engines versus V8



There is no code for what you state.


This is the first thing you have stated that I agree with.


There is no 6 cylinder specific pump, that's why you could not find one.


You would be introducing yet another variable that is going to cause issues. Ford stopped using the frame rail mounted high pressure fuel pump in 1989 on the gas engine F-series trucks. It was overly complicated and now the fuel reservoir is very hard to find and pricey as well.

 

so I’ve heard

part # matches what I picked up. Will check for codes

Replaced it - looked suspect


so, today I got everything back together and started the truck. She started up great, idles smooth. Checked timing after she warmed up & I’m at 10-11 degrees. Took the truck for a ride - great power.

5-10 minutes in I turn around and start to head home thinking I nailed it.

once I start to pull/back into the driveway, let her idle, and i presumably lose air flow - the truck begins to sputter after idling for 5-10 minutes.

I removed the vacuum line off of what I believe to be the fuel pressure regulator, and the truck runs longer (in my head, maybe not) but eventually sputters and stalls out.

I pulled the intake air temp sensor today to check it’s condition - broke upon removal, so it’s been replaced as well.

 

I got a video of the codes. I’ll try and decipher that.

when the truck spits/sputters and finally shuts down - the fuel pump relay is buzzing.

I wanted to make mention of some other things:

battery light is on

battery voltage at idle (via multimeter) 14.2

voltage on the gauge registers on the very low side of the“normal” range. Around 10-11 volts, presumably?

truck idles, albeit smooth, at 1000rpm. down from 1100-1150 prior to IAC replacement. i may just toss a TPS in it for good measure at this point.

truck also stalled when turning the a/c off. the first time it happened, i thought it was a fluke until i replicated it. I tried it while driving, and the truck shut right down.

list of what ive done thus far (some for maintenance):

new coolant temp sensor @ t-stat housing
new intake air temp sensor
distributor (with new cap & rotor)
spark plugs & wires
ignition coil (next to distributor)
TFI on driver fender well
new ignition switch (turned w/o key)
new ignition module under column

 

Pulled code 512

 

So if the aftermarket pump only puts out the 42 psi that the V8 requires the fuel regulator boosts it up to the 60 required by the 6 cyl?
The aftermarket pumps are made on the V8 spec, and don't put out the 60 PSI the 6Cyl needs.
I didn't read the flash codes, I plugged an OBDC reader in, one Snap on, and One Bosh brand, both decoded as an impossible Cyl not firing correctly.
Ford lists separate part numbers for the fuel pump and hanger for the 4.9 L and the V8, they are not visibly the same, having both in my hands at the same time they were not the same size or shape. It could be based on tank configuration, but that was not the information that I received when I spoke with the engineers at Ford Mo Co.
It may be that this is not at all the issue this person is having, I was just sharing what I knew of a similar problem that I had experienced.
I can confirm that the 3 aftermarket fuel pumps I purchased, were all V8 compatible and none put out enough pressure to run the 6Cyl. The correct part number Genuine OEM part worked perfectly and has been going for over 2 years now.
Thanks,
Guy
:-)

 

I think that a code 512 is for Keep Alive Memory fault. It is telling you that it doesn't have a code for you.
Do you have access to a OBDC that you can plug in and see if it is throwing a code there when the events are occurring.
Your truck is a year older than mine and I don't remember when the OBDC change was..... Having a reader when the events are taking place has made a difference for me.
G
:-)

 

512 is a memory only code

512 (M) Memory power (PCM pin 1) was interrupted - Was battery disconnected ?

 

Not by me. I haven’t had the truck long though. And I’ve never pulled codes from it up until yesterday.

Fuel pressure was 40-50PSI but bouncing all over the place. The gauge I had, brand new from Harbor Freight was leaking all over the place.

I’d really like to know why the truck shuts down when I turn the AC off lol

 

Im not sure wat running funny means when hot (at temp or overheating?) And im not sure what your fuel pressure is BUT....if i were you it sounds like you may have a egr system malfunction causing your egr valve to get stuck in the OPEN position.make sure egr valve moves freely an you have good vacuum

 

truck doesn’t overheat. Once it gets
up to operating temperature - it will act up and spit/sputter/stall until it cools down.

i have the old tfi module so I tried to swap it out once the truck shut itself off. The change in module did not allow the truck to start.

I got a new fuel pressure gauge. 50-55psi at idle. Slight Pressure increase With rpm.

replaced the MAP sensor today Just for ****s & giggles. No change - I forgot to see if the truck still shuts itself off when I disengage the AC!

is there a way to keep it in closed loop? Lol