[solomon93]

I have a 72 F100 with a 351W and an AOD tranny. The engine is from a 72 LTD and runs great (I was told it was rebuilt and it does feel that way) and it has a (rebuilt- I was told) Tranny. The truck drives great besides some down shifting trouble sometimes, which i'm sure is TV related. Anyhow, when on the freeway going up a grade for a while at about 65MPH the truck starts jolting and misfiring and i lose all power going at about 20mph max. The truck refuses to down shift during this time most likely because the rpm is so low while the engine is missing and what not. I replaced the plugs,wires,cap,rotor to no avail. The truck drives fine everywhere else. It only happens in the same spot up the freeway where thier is a grade. This part is the most fuel demanding I would say, i'm on WOT most of the time until I hit OD on the tranny then i'm at about 3/4 throttle the rest of the way for 8 miles all uphill. I was thinking the fuel pump? I need some answers or opinions fast. Thanks!

Thanks for the response. I have no temp gauges for the tranny and the motor temp gauge doesn't even work. I'm quite sure the TV cable is a little on the loose side so before I drive it again I will tighten it up a bit more. Any idea why my temp and alternator gauges dont work? Thanks. I check the fuses btw, all are good.

 

[Poppy]

If you sense the problem is the fuel pump, do you have the abilty to check it?
With a pressure guage most fuel pumps for that era should put out (I am pretty sure)5-7 PSI, maybe 7-9 PSI. But if it runs fine the rest of the time, I'll relate an experience I had as a kid. My fuel line (rubber) was dry rotted between the tank and the metal fuel line. It allowed enough fuel to flow to run fairly well, but it balked at highway speeds, and would puke going up a long hill like you describe.

 

[Poppy]

Starving for fuel may also be caused by a clogged fuel filter.

 

[solomon93]

Thanks for the reply. I don't have a fuel pressure gauge. The truck has 2 fuel filters, 1 inline and 1 on the carburetor. I replaced the inline fuel filter and the truck and drove it around a bit, seemed okay but a after i restarted the truck it wasn't running right, I removed the vacuum retard and truck ran good, so now im replacing the distributor. I will check the fuel lines all around, and replace the fuel filter that threads into the carb, do i need a thread sealant for this? Thanks

 

[Poppy]

replace the fuel filter that threads into the carb, do i need a thread sealant for this?

They are usually brass or copper fittings and you need to be careful to not tighten it too much, and strip them. The last time I worked on a carb like that, I don't think they created teflon tape yet. Use of a sealent wouldn't be a bad idea, and if it were me I'd pick one up when I got the fuel filter.

 

[solomon93]

I think i might use some orange silicone on the threads, would that be fine?

 

[Poppy]

I don't know.
I have some RTV Silicone gasket maker by permatex. It appears to be red but some may say that it is orange.

The fine print states that it should not be used for headgasket, or where it may come in contact with gasoline.

So I guess you should read the fine print of whatever you choose to use.

 

[solomon93]

Alright thanks, i will make sure whatever i use is rated for gasoline, i will let you guys know in a few days how things are going.

 

[Poppy]

ok I'll wait to hear back!

 

[solomon93]

Okay I just picked up a re manufactured distributor and a fuel pump, the truck is at storage so on Monday i will be installing them.

 

[Jonzo77]

just out of curiosity, what is the grade of the hill?
the first and only thing that comes to mind is the TV cable... AOD's are touchy about the cable setting, i mean REALLY touchy

 

[Jonzo77]

Lincolns OnLine | Tech Tips and Articles
the above link has plenty of info on how to do the adjustment, and then some...

 

[Poppy]

Jonzo... that is a great find!
You da man! :thumbsup:

 

[solomon93]

Going to be dropping in the parts in a few hours. Thanks For the link, but it is to no help. I have looked at that link about a million times, but my tv setup is different. I have a LOKAR brand setup. Looks just like this http://www.transmissioncenter.org/HPIM1778.JPG
You have to loosen the allen on it and pull the cable and then tighten the allen again. I know as long as the cable is tight it should be fine, it when it is loose it acts up. But i do plan on taking the truck to a transmission shop to have the cable adjusted. Thanks Guys, will write back later. It's a reasonable grade goes from 2000ft to 4000ft elevation in only 6 miles

 

[Jonzo77]

It's a reasonable grade goes from 2000ft to 4000ft elevation in only 6 miles

i was wondering about that because i was starting to get the feeling it was your carb... something about the floats getting all screwed up, or something. i don't remember what it's called, but when i do, you'll be the first to know...

 

[solomon93]

I rebuilt the carb maybe 150 miles ago. I think the float level might be a little low though. I didn't manage to throw those parts on today, but i will tomorrow. I will update you tomorrow and let you know how it goes.

 

[solomon93]

UPDATE, Well the old dizzy was shot it had terrible bushings and was destroying the cap. The new one went in nicely and so did the fuel pump.I also threw the carb fuel filter on all with ease. I did a compression teat on all cylinders going from 1-8 it goes as following (125,145,125,125,130,130,130,130) Some plugs looked lean and other rich. I was told this may be pointing to a Bad Cam or Stretched Studs. The engine Idles great but once revved it misses badly and looses all power. No matter if i Advance or decrease the timing. No vacuum leaks and points are set to .017. New Cap and used Rotor in good shape. Looks like I need a cam or heads?

 

[Poppy]

I am far from the expert when it comes to this, but those numbers look a little low to me, but even. You could try putting a table spoon or two of oil in each of the cylinders and see if the compression raises. If it does then the problem is likely with worn rings.

 

[solomon93]

I was told the compression was very good, although 160 is like new. So my engine is in very reasonable condition, the bottom end at least. I will do the oil trick to check the rings, but i feel it may be the heads or cam.

 

[Poppy]

THere are certainly better mechanics on here than me, hopefully if they see something I am missing they'll jump in.

I don't know about cams, so I don't know if the advise you were given is accurate, I guess it could be.

On the other hand, if your points are weak, ie the spring steel that closes them is weak or fatigued, you could have "floating" points when you rev her up. Just a thought.