The problem with the small leak that cross fills the tank is that this leak won't allow the fuel system to pressurize correctly, causing some stalling and rough running conditions. Aliens8mycow seems to think that when the bad tank is full the truck runs better and when he removes some fuel from it then it runs worse. I think that is because with the tank very full the fuel now has nowhere else to go so the system will now pressurize.

 

...you know my theories are always half-baked!

I do think that it makes a difference, and have repeated it several times with the same results. I just need to get busy working on the front tank.

 

Hello all,

I cranked the truck, pulled the vacuum line at the manifold side and covered the hole I made. There was an increase in RPM, but I hesitate to even try to say how much. I went back and forth a few times, and it always seems to rev a little when I pull the line. FWIW, the drop in RPM on replacing the line is (to me at least) less obvious than the increase on pulling it. Remembering something I was told elsewhere, and not seeing or smelling any gas, I sucked on the line a little, and was able to slightly slow the engine.

These are not huge changes, but they are in the direction I was told to expect of an ok regulator. Is that enough, or do you want me to quantify the changes?

I guess it is time to do some more test driving. I have no reason to think it is going to run less rough than it did, but maybe I can build enough confidence for a trip to Autozone to look for any new codes that might have been stored (the check light is off though??) and to see if I can detect any cross-filling into the rear tank.

I have a new fuel filter. Should I change that "now" or wait until after I drop the tank and replace the pump? I am (finally) getting ready to just tear into that, but admit that I might benefit from a small transmission jack, and really should get new lines that attach to the tank.

Autozone threw me over to the dealer for the lines. Is that the right thing to do, or do you recommend any on-line sources? I will also call Advanced, as they sometimes have things AZ does not.

Re jacks, anybody know what a 5-speed manual transmission for an F-150 weighs? Harbour Freight sells a couple of low-profile tranny jacks that would be nice to have for this, and would be no-brainer if they would also be useful to me (much) later as an actual tranny jack. The cheap ones max out at 800 lb; there are low-profile jacks that can handle up to 1200 lb, but they cost just enough to make me want to wait until I need that capacity.

A sad state of affairs: I called around looking for suitable jacks for sale locally. The guy at Pep Boys had never heard of a transmission jack .

Bill

 

No quantification necessary - if fuel wasn't coming out through the vacuum line, the regulator is probably good to go.

If you are going to change the fuel pump, I'd wait until then to replace the filter.

The dealer may not have the fuel lines anymore either, but they might. They will take every penny that you have if they do stock them...

I think you're safe with an 800lb tranny jack.

Pep Boys sux...

For what it's worth, I mentioned earlier in your post about having similar issues, cross filling, unreliable fuel pressure, stuttering, etc. A few days ago, due to my own stupidity, I had to replace a fuel filler cap. Replaced both just for grins... My truck hasn't given me a bit of trouble since - no promises, but that might be the cheap and easy solution for you too!

 

You are not the first to suggest a gas cap change. The guy who suggested it was emphatic about it, but his description didn't seem to match all the facts, and I do not know him, so there is no track record.

Can you explain the cross-filling based on the caps? Did you notice anything different that I could use to decide on whether I should replace them? I should probably just do it though. Until I see cross-filling, I'm hesitant to replace the pump.

Good news about the tranny jack. Since I seem to be stalling for a reason now (as opposed to just stalling), it makes sense to get something that will be useful and give me good control over the tank should I need to drop it.

About the lines, I called Advance and heard something interesting: they sell some of the fittings, and they sell high-pressure fuel hose. So, it might be possible to recreate the hoses with good parts w/o settling the national debt in Ford's favor. Worth a try. I will stop by there some time to see what they have.

Test drive report: the truck did fairly well today. I took it around the subdivision w/o incident, so I went to 45 mph territory, and it was still fine. I decided to go for the 4 mile trip to AutoZone. On the way, I stopped for a red light, and noted the check engine light was on; it had stalled. It cranked immediately, and that was the last trouble I had.

AZ scanned it: no codes. I ran the pumps for him. He was not concerned about the difference in pitch, and mentioned the different shape tanks. He is not the first to point that out, and his "they sound fine" means a good bit to me. I then cranked it and pulled the vacuum line for him. The change in speed is not terribly impressive, but it is there, and you seem happy that it's not spitting gasoline. I am still curious whether we can get a report from anyone who has changed a regulator on a 4.9; specifically, did the manifold need to come off to do it? Again, I'll wait on that for now.

He commented that it felt and looked rough to him, and he went straight to the plugs and wires. I have some parts to change now. I bought more than he was trying to sell at one shot, but he said to bring back anything that I don't use. My car went through a period of eating spark plug wires. I finally nagged my mechanic enough that he replaced a suspect spark plug, and the problem stopped. I forget where I read it, but a cracked plug can look pretty uninviting at high frequencies, and my theory is that the juice found a better place to go until we lost the plug. I have NO idea whether that is really what happened, so buyer beware. However, that left me a soft touch for replacing cheap distributor parts when they look worn.

Thanks!

Bill

 

I don't know about the cross filling. The thing I've noticed is that my truck doesn't go through periods of what feels like it's starving for fuel and losing power. I haven't had gas leaking out of the filler neck since changing the caps, so maybe it has helped the cross-filling too?

You may have to buy a tool or two in addition to lines and fittings to make new fuel lines, but that's about the cheapest way to do it. You can also route them where you want them.

I don't see why the manifold would need to come off to change the fuel pressure regulator, but there are some that have the fuel line bent right over one of the screws making it hard to get apart.

Plugs and wires are probably a great idea if they are old anyway. When you change the plugs, keep them in order so that you can inspect for clues to what's going on. You could have a bad/clogged injector causing the truck to run rough or miss on one cylinder.

 

You don't need to replace the lines and I don't recommend it unless they are leaking. They are plastic lines on these trucks, that's why you are having trouble finding them. You can't just patch a section, you have to replace the whole line from one fitting to another.

The regulator sounds fine.

I would go ahead and change the filter now. They are cheap if you have to buy another, and you could get lucky and that will fix it preventing you from having to drop the tanks.

The 5 speed weighs about 200 pounds, give or take.

The fuel pumps may work perfectly well and would sound fine but the bad valve wouldn't change any of that.

 

The screws like they are reasonably accessible. Turning the hex wrench might be another matter, but inserting the tool should be possible. If I were to have a problem, I would expect it to be the regulator hitting the manifold before it can get free of the rail. Hopefully it would be possible to turn it a little before it collides?? I have no idea how high I would have to lift it before it disengages, hence the question.

But now that you mention it, access to the screws is something that comes up; I have not heard of lack of vertical clearance, so it might be easy to do.


Excellent idea!!! Thanks for mentioning that _before_ I managed to lose track of the order.

Bill

 

Sounds good - I'll do it along with the tune up.


Cool. One guy put it as high as 300 lb, but nothing that should overwhelm even the smaller of the two jacks I am considering. I have no immediate plans to pull any transmissions, but since it can do that too, it seems like a good purchase.


Understood, but the difference in sound between the two pumps caught my attention, so I got a more experienced set of ears to check on them. Since they sounded different, that might have meant that one was good and one was bad.

Thanks,

Bill