1981 straight six manual 4x4 project

On Monday night I towed our camper to Golden Valley. Unlike our recreational trip over Christmas, it was packed with household items and was very much heavier. The truck bed was also loaded with cargo. The 12:1 first gear starts were quite rough on the clutch, and even with the close ratio transmission I was having to rev it up pretty good in between shifts. I was definitely working it. Likewise the braking was noticeably compromised. Hydroboost or not, the F150 pads and shoes only have so much surface area. My mpg calculation was a surprising 12.37mpg. This was better than the trip over Christmas, but perhaps the seasonal fuel blend difference played a part. Perhaps it is just fill up variation.

Truth be told, the truck isn’t running all that great. Before the tow I felt some more stalling/starving, and the idle is tougher than I like. It does not start as easy as it should. It needs some work but unfortunately the show must go on. I also noticed it lost some oil, and I thought I was catching a wiff of hot oil smell while driving, but I looked it over and I can’t see any obvious leaks. I will have to keep an eye on this. I will be putting quite a few miles on the truck this month.

The home purchase that we were working on fell through. It was a investor/foreclosure thing, and turned out the seller did not have titles to the mobile halves. Big problem and not worth the hassle. We ended up buying another parcel a couple of miles away. The house is only a single wide, but is ready to live in with a little bit of maintenance. The lot is over twice the size and has a nice chain link fence around the house. The main downfall is it is a water haul property... but the peace and the views make it worth it. Eventually we will look into drilling a private well, but until then the ‘81 will be our water hauler. I went to Mohave Valley to buy a couple of haul tanks. And no, I don’t intend to fill two 275 gallon totes in the bed of the truck! I have a utility trailer that will shoulder some of the weight...

Ford F834 wrote

Eventually we will look into drilling a private well, but until then the ‘81 will be our water hauler. I went to Mohave Valley to buy a couple of haul tanks. And no, I don’t intend to fill two 275 gallon totes in the bed of the truck! I have a utility trailer that will shoulder some of the weight...

~4400#!

David, this truck spent a great deal of it’s life with a 325 gallon low profile water haul tank in the bed (2,600 lbs) and had to haul it over some not-so-nice roads. A single 275 gallon tank is still over the GVWR but will be just fine on the low speed 1-mile route. The trailer can easily handle the second tank, maybe even a third? I will have to see how it handles. Because of the dense nature of water the load behaves much better than bulkier loads of comparable weight. That’s still no excuse for gross overloading but as stated on a slow rural route the safety margin is forgiving...

For you, Jonathan!

http://www.thedetroitbureau.com/wp-content/uploads/2012/02/Beverly-Hillbillies-with-Car.jpg

Jonathan - Looks like you are making progress!  And a one mile drive should be easy to get water.  

The ‘81 has been working it’s 9” rear end off last week. It needs work but it’s hanging in there and doing its job in the face of adversity.

I replaced the fuel pump and filter as I worried that it might be the cause of the stalling out symptoms that happened randomly... and I did not want to experience what happened to David if the diaphragm was failing. After replacing the pump I could not get the hard line to seal, so I bought a new one and replaced that too.

I have not had any more stalling but I still want to rebuild the carb. The idle is all over the place and not smooth like it was. I turned in the warm idle screw so it wouldn’t idle down too far on me, and it now varies between 500 and 1,000 rpm with no throttle. I’m also noticing that it is sometimes dieseling or runnin-on after I turn the key off but not all the time. Pretty much sounds like I have a vacuum leak and erratic advance? I bought the gallon of chem dip and the carb kit... now I just need a spare day off ha ha ha... not for a while 😕

When I hauled the load of scrap, I was on my way to work first, then junkyard in the morning after my shift. I ran the speedometer app, and across some of the flats I ran as fast as 80 mph, which is the highest I have taken it. It felt pretty good and the tach was showing 2,500 rpm. A little further along the route I backed off on my speed because the freeze/thaw road damage creates rough spots. The truck does not handle these well at all. The tires bounce and you loose control in an instant. I doubt that there is much that can be done for that except drive slower. I noticed this on the wash board roads in Death Valley also. Some Baja outfitted trucks were racing down the washboard going 60? mph or so and seemed unaffected. But their suspension is not for hauling, and surely soft aired down tires help a lot. You just can’t have it both ways.

I checked my mileage at my last fill up and figured 15.91 mpg. Not bad considering the faster highway driving, mountains and light hauling that created some wind drag if nothing else.

Not much of a build update... but checking in nonetheless.

An idle speed that is all over the map is sometimes because of a worn throttle shaft or carb housing.  It lets the throttle plate stop at different places depending on where the shaft is in the carb.  And, it lets more or less air in around the shaft as well.

You can try spraying brake cleaner around the throttle shaft and see if it sucks it in and speeds up the idle.  Or see if the shaft will wiggle - after taking the return spring off.

As for 80 MPH, Big Blue would be turning 3100 RPM.  Who needs to turn a 460 that fast???

And basically 16 MPG in those conditions is nothing be ashamed of.  But, with some tuning maybe you can bring it up a bit?

I’ll check that on the carb when I can. This is just a JY take off after all. I know I can improve the mpg and overall performance, but for now I’m just grateful that it starts and runs and is reasonably reliable. And I’m grateful that I have it to the point that it is because we are sure using it...

Good old 300 engine: gasoline diesel!

I think may have I jinxed myself by saying the truck wasn’t perfect but was getting by. I was hauling a load of household stuff yesterday and stopped for coffee on my usual route to I-17. Just as I pulled out the stalling was back. A few throttle taps and it cleared up and I was on my way.

But later on the I-17 it came back with a vengeance and was stalling more than running. But by the time I found a safe spot to pull over it cleared up again so I continued up the mountain. It was running fine for about 15 miles then went south. I managed to milk it to the off ramp at Munds Park coasted to a wide spot away from passing semi trucks. I mounted my spare carburetor and tried again... about 1/4 mile up the on ramp it was already stalling again. I backed up to a safe spot for some more checking.

I decided to replace the piece of fuel line between the tank and the hard line in the frame rail. I had not replaced this previously because it looked okay, and the stock one has a hard plastic liner. But I couldn’t think of what else to try. It did have some little cuts on the soft attaching ends, so I thought ah ha... I found ~a problem. The truck started and ran 145 miles with no stalling. I thought I had something. But as I came into Kingman I noticed by fuel was pretty low so I stopped and bought gas. About 1/4 mile up the road the stalling was back.

To re-cap. The sending unit is new. The soft line from the tank to the hard line is new. The tank selector is bypassed with a new piece of fuel line. The fuel line to the lift pump is new. I just replaced the lift pump, steel line, and inline filter to the carb and that didn’t change anything. And two different carbs just did exactly the same thing. It really feels like fuel starvation, but I am running out of ideas.

This morning I switched carburetors again, if for no other reason than I wanted the one that generally runs better.

I tried changing the DSII module, because they can do some weird stuff. (Still stalling).

I tried swapping on a spare ignition coil, as they can do some odd things as well. (Still stalling).

What am I missing? What should I try next?

Sounds like you are all over it. Frustrating! I don't remember all that you did, but have you checked the fuel tank vent?

I don't know if your truck is a vented cap or a vent line. Maybe drive it with the cap loose.

Good idea! The truck had a charcoal canister, but I removed that and placed an open vent with the little plastic tip like they used for non-emissions and diesel models. Anyway, driving with the cap loose is very easy to try! 👍

When I first got my truck the emissions were a mess. I found the vent line hanging there covered in dirt!

That’s a good test. But if it still falters you should look closely at the wiring of the ignition pickup in the dizzy. Then consider replacing the pickup itself.

Nice try but no cigar. Still stalling with the gas cap removed 😔

I sure don’t want to, but I might have to drop the tank and take a look.

Gary Lewis wrote

That’s a good test. But if it still falters you should look closely at the wiring of the ignition pickup in the dizzy. Then consider replacing the pickup itself.

What exactly am I looking for Gary? I do have a spare distributor, maybe I should just swap and see what it does?

Bare wires that might short when the vacuum or mechanical advance moves them.

And swapping the dizzy might be a good idea.

Thanks. I don’t see anything obvious amiss there, but I think tomorrow I will swap distributors just to see what happens. It’s not a pristine unit, but it costs nothing to try it. The 4x4 donor gave me a lot of spare parts which can come in handy for troubleshooting.

I switched the distributor with my old spare and the truck would not start or run at all. I was very careful to find TDC, but I was hearing slight back-fire from the muffler while cranking. So I decided to try it 180* just in case I screwed it up. It would not start or run there either. I put the other distributor (that I have been running) back in and re timed it. It’s running again. I hauled a load of water and so far no stalling, but that’s the nature of an intermittent problem. I have not fixed anything so I know it will come back. I wanted to run and buy a new one, but of course no one here stocks it, and if I buy a new one I am thinking that I should choose carefully as there are other options besides the rebuilt stock ones. Mine looks to be in great shape, and honestly I don’t think it’s my problem since it does not run rough or misfire, but I’m running thin on ideas.

It sounds like the pickup in the spare dizzy is bad.  That's about all it could be.

And I agree you've not fixed anything, so the problem will come back.  However, if you moved a wire that was broken or shorting then it might not come back until you move the wires again.

The pickup modules can start failing when they get hot.  And from what I've read they quit and then come back again pretty quickly.  But it is all or nothing.  No bogging down as if running out of fuel.  Just on/off.