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Hole in the fuel line? That's like sucking on a straw with a hole in it. If you have a Mity Vac, see if you can draw fuel from the tank just before the pump.

I would keep the factory tank. Nothing about a fuel cell prevents you from using the original fuel pump, but why?

tgreese wrote: ↑Sun Jan 29, 2023 9:07 am Hole in the fuel line? That's like sucking on a straw with a hole in it. If you have a Mity Vac, see if you can draw fuel from the tank just before the pump.

I would keep the factory tank. Nothing about a fuel cell prevents you from using the original fuel pump, but why?

Don’t have the right kind of vac, but will see if I can source something if needed. And happy to have kept the tank in the end since the exhaust was easy enough to move to a safe distance.

My dad decided to add a helper pump on the line upstream from the mechanical pump that is good for 6psi, but still can’t get fuel downstream. He has an A/C vac, and with 60psi from that, he can get fuel from the tank. Could it be a kink near the tank, perhaps after reinstalling, or are we missing something?

tgreese was right: found a hole halfway down the frame in the fuel line. Replaced and all good now, was just hard to find since it was so small.

Replaced the water pump and added a shroud from BJs. All seems well now. Had its maiden voyage to town for gas and back.

At this point, I’m planning to replace front and rear diff oil and look into the driveshafts. The axles take 75w90, correct? Do I need to determine if rear is LSD and takes synthetic, or should that not be a factor?

I buy gear oil by the gallon at Walmart for these axles. 85W90 GL-5 dino oil. GL-5 is not for our manual transmissions, but fine for axles. I would not put synthetic in; might be ok, but they were designed for dino oil. Synthetic is more expensive, no advantage.

A LSD axle will have a small tag that indicates it needs special oil. Or take the cover off and look. Post a pic if you can't recognize the axle type. Open vs others is pretty obvious by inspection. Again, not synthetic; dino oil. If it's LSD, you need a friction modifier additive that's mixed with the gear oil. Comes in a separate tube at the parts store or online. Year, model, equipment? Quadratrac? Put it in your signature file and it will appear in every post.

tgreese wrote: ↑Thu Feb 23, 2023 11:43 am I buy gear oil by the gallon at Walmart for these axles. 85W90 GL-5 dino oil. GL-5 is not for our manual transmissions, but fine for axles. I would not put synthetic in; might be ok, but they were designed for dino oil. Synthetic is more expensive, no advantage.

A LSD axle will have a small tag that indicates it needs special oil. Or take the cover off and look. Post a pic if you can't recognize the axle type. Open vs others is pretty obvious by inspection. Again, not synthetic; dino oil. If it's LSD, you need a friction modifier additive that's mixed with the gear oil. Comes in a separate tube at the parts store or online. Year, model, equipment? Quadratrac? Put it in your signature file and it will appear in every post.

Signature added with what I'm aware. Not yet certain if still Quadratrac or if it has part-time kit. Below are photos from before work began of the rear and front axles respectively; if I need to get better ones, I'll do so when I go visit it next.

https://www.dropbox.com/s/apr1odymwze0d ... S.jpg?dl=0
https://www.dropbox.com/s/3s34rgnvb3x41 ... S.jpg?dl=0

I ask about Quadratrac because they were all delivered with open differentials. These will all take the plain GL-5 gear oil, no additive needed. Part-time won't change that. It's still a Quadratrac even with a part-time kit. There is a remote possibility that a PO changed one or both of the axles to a LSD or locker - remote possibility - take the cover off and look. Buy the gasket and your oil first. If you need additive - you can add it after you put the cover back and oil in.

Front and rear Dana 44s, just like it shows in your '79 TSM. Tag is missing from the front axle; likely a PO pulled the cover off and did not put the tag back. No need for new axles IMO, unless you plan to abuse the Jeep. Especially with open axles.

Since the cover for the rear axle is bent in one spot, this'll be a good opportunity to go ahead and replace both front and rear covers, so I'll get a look inside them and get some photos, then replace the oil appropriately.

Seems the gas feed problem is still present. Now determined that it runs and drives fine so long as it has above 3/4 tank of gas - soon as it gets at or beneath that, it starts choking and eventually can't get any fuel from the tank. The sending unit was replaced when the tank was dropped with this unit. Could there be an issue with the sending unit? The pickup tube seemed to be fixed-position, so I can't imagine it's not able to pull from the lower part of the tank like it should. No further leaks found either.

If it’s fine at 3/4 plus and the supply line isn’t connected to the return line, shouldn’t run at all like that but is possible, there’s a hole in the pickup tube. new don’t make it automatically good.

Yeller wrote: ↑Fri Mar 03, 2023 12:57 pm If it’s fine at 3/4 plus and the supply line isn’t connected to the return line, shouldn’t run at all like that but is possible, there’s a hole in the pickup tube. new don’t make it automatically good.

Kind of what I was wondering. Also, there was a segment of hose on the end of the pickup tube of the original sending unit that reached further down into the tank. Was that supposed to be installed to the new unit? There were no instructions stating as such, so the new unit was installed without it.

All '79s came with FTVC (fuel tank vapor recovery, the charcoal canister and plumbing) according to the '79 TSM. The original gas cap is sealed, no vent. If your FTVC has been removed and the lines plugged, the fuel pump is pulling a vacuum on the gas tank. At some point the lower pressure in the tank will be too much for the pump and it will stop pumping.

Read the TSM. Fuel tank and FTVC shown there. Compare to what you have.

Additionally, there should be a screen on the end of the sender, not a piece of hose. Jeep PN 5357421. Should have come with the sender - it's shown in BJ's picture - and it does extend the pickup further down.

I found one aspect on all three of mine is needed to replace every rubber vacuum hose in the entire truck!
100% of it, everywhere!
Yours should have the three metal tubes, on Pass side, behind intake to the trans diaphragm area.
Those you should flush to make sure they are not crapped clogged up or possible leaking from rust holes.
These rigs are notorious known for their rubber hoses have leaks somewhere, so I suggest shotgun it.
Chance previous owner neglected this, as typical.

As tgreese said, if you don't have a vented cap on it and aren't running the recovery system, that's a problem. When I put the '79 tank and filler in my Wag, I thought the cap was vented, but it was not. I wound up doing a kind of stupid trick to it to vent it (don't worry it's not like it's gonna spray gas everywhere), but it works REALLY well. Although mine still ran ok w/o the vented cap--I just had to remember to take the cap loose after every trip to make it not implode something. Eventually the pickup tube gasket gave out, and then when I dropped the tank I fixed the vent.

And if you're worried about the vacuum hoses, a) the hoses are cheap, just do them one at a time, or b) disconnect and plug all of the vacuum ports on the carb and intake, and see if it runs OK then.

As others said, check all the rubber and the steel--make sure there aren't any leaks and that everything's clean.

Working on timing at the moment. Didn’t find the spec for timing the 360 in the TSM. Does anyone have the timing info for this engine, or am I overlooking it? Truck operates within 1000ft of sea level.

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tgreese wrote: ↑Wed Apr 19, 2023 9:06 amPage 1A-21.

Thanks tgreese, I’m as blind as a bat.

New stainless steel fuel feed and return lines from Inline Tube plus new applicable rubber hoses installed. Charcoal canister bypassed and vent lines sealed, using a vented gas cap now. Timing is adjusted. My dad also found a broken ground strap between the engine block and frame, so that’s been replaced as well.

Despite a new radiator, thermostat, temp sensor, fan shroud, fan clutch, and water pump, still having an issue with the temperature - or at least what the gauge reads. Every so often the gauge will quickly climb to max, and sometimes it slowly builds up to max. However, laser temp gauge to coolant reads right around 160. Could the gauge be faulty? Radiator has been burped on an incline while running to and past warm, and coolant in radiator now stays clean and no bubbles in oil still, so thinking head gasket is now ruled out.

Faulty gauge, sender or wiring is highly suspect. The gauges are more of a hint than reality. In my truck it will fluctuate over 1/2 of its sweep over a 20 degree spread. I don’t give it much thought unless it’s all the way over, which it has never done.

Yeller wrote: ↑Sat Apr 22, 2023 11:09 am Faulty gauge, sender or wiring is highly suspect. The gauges are more of a hint than reality. In my truck it will fluctuate over 1/2 of its sweep over a 20 degree spread. I don’t give it much thought unless it’s all the way over, which it has never done.

Got it. Now that the fuel gauge is working, it’s been observed that on occasion, both the temp and gas gauge will suddenly spike to max at the same time. Could a bad ground to the cluster cause that?

Yes bad ground would be my go to for that.

Could be a faulty voltage regulator thingy too. The gauges work on 5-6 volts, can’t remember if the 79 cluster is that way or not.