I hope I'm in the correct area for this.

I have a '94 F150 Extended Cab with dual gas tanks. (302 V8). The truck has begun to cut out while driving on the highway, and at times I will lose power and the Check Engine light will come on. With 194,000 miles, I'm thinking it may be the fuel pump. So I have 2 questions:

1) Are there 2 fuel pumps?
2) where are they located?

 

First, welcome to the site!

Not sure when the change in fuel pump strategy was made - the older fuel-injected vehicles had low-pressure pumps in the tanks and a high pressure pump along the inside of the driver-side frame rail, just about under the driver seat/floorboard area. The newer trucks have only the pump(s) in the tank(s).

Suggest to do a bit more troubleshooting before jumping into the labor and expense of a fuel pump replacement:
* Get the computer code pulled to get a better idea of just what the computer ain't liking.
* Does this cutting-out occur on both tanks, on only when on one particular tank?
* How's the fuel filter - when was the last time it was changed? While you're at it, how's the air filter look?
* During the fuel rail charge when the ignition switch is first rolled to the ON position, do things sound normal for the fuel pump's 2-second charging cycle, or is there a different buzz/whirr sound?

 

if I only had a way.....

I'm going to test that tomight. I hadn't given that a thought until after I posted this message.

That was supposed to have been changed in the spring when I took it in for a ton of work.

I don't recall hearing anything, but then I never really have paid that much attention. I was wondering if there was air in the fuel line somehow and if that would affect it.

This is going to sound really wierd, but it seeme to act up more when I'm bucking a strong head wind. Yesterday morning coming to work I was hitting about a 20mph head wind and that's when it died (or apparently died when the Check Engine light came on), and it hiccupped a couple of times before that. On the way home I had one small hiccup - with a tail wind.

Sat night driving about the same distance it only hiccupped once. It ran really well until that. It was also hard to start Sat night - I had to pump the accelerater and it finally caught and started.

 

According to my Chiltons book - '89 was the last year for the low/high pressure pumps (figures!) - after that it was the in-tank pump only.

Not sure exactly when the change was made between the OBD-I and OBD-II control systems - I was thinking 1996????

AutoZone reads codes for free, however, other members have pointed out that this service is only for the OBD-II systems - may check with your local chain parts store on their capabilities and free services.

At any rate, most garages will read the codes for a fee. An OBD-I reader can be picked up for about $30-$35 but may take some scrounging around to find one - this is likely at or less than what a shop would charge. An OBD-II reader goes for around $150 from what I've seen. If you do a lot of your own work, a code reader is an excellent addition to the toolbox for future use.

Air in the lines will make the fuel charging process sound different. After I change a fuel filter, I will cycle the key to ON several times until the priming process gets back to sounding like its normal self, which I take as the sign that the fuel line has been purged of air.

As far as the headwind thing - that would correlate with a fuel-starvation issue as a possible cause. Another cause to keep tucked in the back of the mind is that the fuel-pressure regulator may be acting up.

Suggest to get the codes read - it may indicate a whole nuther direction, or may validate what the current thinking is. I avoid blindly replacing parts - end up spending a lot of money on replacing parts that were good, as well as taking the risk that the unnecessary new part may be bad out of the box thus increasing the degree of difficulty by adding yet another problem to troubleshoot.

 

I took it by a shop last night for them to look at and hopefully pull some codes off. I'll post what they tell me.

 

Yes, the switch to OBD-II was in 1996. I have a 96 F150 and it has the jack to hook up the reader under the dash by the glovebox.

 

The shop called late yesterday afternoon. The codes indicate a bad EGR and throttle switch (if I remember correctly).

Now, here's the deal that really cheeses me. This past Spring I took it this same shop because of the way is was behaving - dying at stopsigns and running bad. I also had them fix the A/C, check the u-joints, and replace the rear main seal. They checked the brakes and told me I needed new shoes on the rear. That I didn't doubt because of the mileage since the last time I did them. Normally I take care of all that stuff myself, but I just don't have a place to work on it or the time.

Well, a few weeks ago the brake light came on, so I checked the reservoir and sure enough it was low. So, when I took it in I told them about that and the stalling, they agreed to check it all at no charge. Yesterday, along with needing to replace the EGR and throttle switch, they said my axle seal was leaking and thats where the fluid was coming from on the tire. So I said that's all well and good, but where's my brake fluid going? They are going to go back and revisit that. I suspect a leaking seal on the wheel cylinder that when the brakes are applied is spraying fluid near the axle and running out the backside making them think it's an axle seal. I'm probably wrong, but that would be my guess.

The good news is they are replacing the EGR and throttle switch and just charging me parts.

Thanks for the ear, guys.

 

Glad you're making progress.

They're likely talking about the throttle position sensor (TPS), located at the bottom of the throttle body, attached to the butterfly shaft. Its failure will cause some severe engine bucking and snorting problems whenever the throttle position is changed, but if the throttle is held constant, things should catch up and even out.

One thing to keep in mind with the EGR valve troubles is the EGR solenoid - the assembly that sends the vacuum to the EGR valve, located at the driver-side rear of the intake manifold - just follow the vacuum hoses. Had an occurence where a dinky foam air filter inside this solenoid plugged up and resulting in EGR codes.

Just based on what you've shared, I suggest to consider finding another garage. Sounds like they may be good at fixing problems, perhaps just jumping the gun a bit towards identifying the right problem to fix. If you weren't there to point things out, you may have ended up with a new axle seal and an old leak.

You may also have a master cylinder leaking. This is sometimes indicated by the paint staining or rust path on the booster below the master cylinder. Also, if you hold a firm brake pedal, and the pedal slowly drops - another sign of a brake system leak.

At any rate, sounds like the ball is rolling towards getting things back in shape. Keep us posted on any new and unusual findings!

 

It could be a brake seal in the rear, or it could be a leak in the steel brake lines. I recently had to have the front brake tube replaced due to a hole rusting thru on the driver's side. That was what was causing my fluid to leak out.

Good luck on the brakes.

 

Well, the bright folks at the shop just called. Seems when they do a brake job they don't rebuild the wheel cylinder at the same time they replace the shoes and turn the drums. Care to guess what's leaking now? Oh, and they said it looked fine when they did the brakes, so they didn't bother to change out the seals (obviously didn't hone the cylinder either). According to them, the leaking axle seal is eating away at the wheel cylinder seal and causing the leak. Uh, huh.

I may have to borrow my neighbors driveway to fix this one the way it's supposed to be.