My wife and I bought a 1976 Jeep CJ7 at the Mecum auction a few weeks ago. It's been restored and upgraded. Engine is a 360ci with built heads, exhaust, etc... When we went to bring it home from the auction, it was cranky to start. It was cold outside and apparently all Mecum cars are run across the block almost out of fuel. We got it fired up and went to the gas station 1/2 mile away. Filled it up and drove it 30 miles home no problem. It was great. Went out a few days later to drive it and... sad trombone... it wouldn't start.
It will catch with starting fluid but won't run. I put a new fuel filter in for good measure. Nada. I have removed the fuel pump but am struggling to identify it. Like I said, engine is a 360, supposedly "new" but I don't know from what. Local parts stores are clueless. Any identification on this? Google says it's an Airtex??
Will the fuel pump from a 304 fit?
(rockauto pic)
Never mind, it looks like this Carter fuel pump. Carter pump at Summit which seems to be # M4656 and 4656BD is on the side of your pump.
Bummer that you just bought it and are spending money on it.
IMO mechanical fuel pumps "work" but the diaphragms always rupture at the worst time, and running the fuel suction line by the exhaust is a recipe for vapor lock. If the fuel pump is bad, then this is the universe telling you to put an electric pump in.
THAT SAID. There should have been enough fuel in the carb for it to run for at least a little while. I wonder if you don't actually have a stuck needle and seat, or a fuel leak into the engine if you have a Q jet. What kind of carburetor is it?
The Jeep J10 came with a 360 in the mid 70s. Looking on RockAuto lots of pumps available for them. Might have to adapt your fuel lines but not a big deal.
Noddaz said:
Will the fuel pump from a 304 fit?
(rockauto pic)
Never mind, it looks like this Carter fuel pump. Carter pump at Summit which seems to be # M4656 and 4656BD is on the side of your pump.
Bummer that you just bought it and are spending money on it.
Yes. Will fit. Bummer? It says right on it Just Empty Every.....
Welcome to Jeep. The struggle is real. I have basically the same Jeep CJ7, 1977 with a 360 from '84.
Current thinking is that there are no good mechanical pumps. I had the same style Carter until recently, I'll have to look and see if it's the same number. The arm looks different than I remember. I went back to a factory style like above from RA.
What ignition is it? If it's an HEI conversion, they are notorious for stripping the gear at the camshaft, which will cause erratic timing until it's worn out and fails. Usually within a couple hundred miles. Similar symptoms.
The fuel filter, if it's stock, should have a smaller return nipple on the carb side. It needs to be at the 12 o'clock position or the fuel will all drain back to the tank. It should be a Motorcraft 2150 2 barrel carb, which is actually a great carb. But it may be different after an engine swap.
That being said... mine does the same thing. I just crank and pump the hell out of it. It may take a minute or 2, but it always starts.
Good luck! And we need pictures
There has been a huge rash of bad mechanical fuel pumps for the last few years, especially anything AMC/Jeep. Luckily yours is at least rebuildable.
Are you sure it's bad? If you move the arm, does it pull suction?
Speaking from experience, just ditch it and go with a low pressure external electric mounted as close to the tank as you reasonably can. Up under the Jeep like that you won't hear it much and it'll work well. The generic Pureolator brand I used was flawless for years. If you don't feel like making a block-off plate you can just leave the mechanical one hanging there.
Also, if that 360 is decent, watch it. That'll be a bit of a rocket in a CJ and will quickly write checks the chassis and brakes can't cash.
Steve_Jones said:
Are you sure it's bad? If you move the arm, does it pull suction?
Can you manipulate a mechanical fuel pump fast enough to make a suction? I haven't had any luck with that testing method even on pumps that turned out to be good.
In reply to A 401 CJ :
If you put a finger on the "in" nipple, you can usually move the arm enough to get it to hold your finger there if it's good.
Never messed with a mechanical pump before. Is conversion to electric as simple as putting one in the line near the tank and then leaving the old mechanical one in place?
Here's the Jeep, the price is after all the fees
https://www.mecum.com/lots/1101601/1976-jeep-cj-7/?aa_id=534210-0
In reply to SKJSS (formerly Klayfish) :
They make block off plates vs leaving the old one there. I'd install the old one, put a line on the out to a jar, and see if it's pumping before I started tossing parts at it. Verify it's bad. You can also pop it apart and see if the diaphragm is good, that is the part that breaks. I'd lean towards vacuum leak in the fuel line vs bad pump first, it's common.
In reply to Steve_Jones :
Yep, I planned to do that this morning. Maybe it's possible there was a vacuum leak at the gasket?? When I pulled the pump off, the gasket looked sad and broke into two pieces.
SKJSS (formerly Klayfish) said:
Never messed with a mechanical pump before. Is conversion to electric as simple as putting one in the line near the tank and then leaving the old mechanical one in place?
Here's the Jeep, the price is after all the fees
https://www.mecum.com/lots/1101601/1976-jeep-cj-7/?aa_id=534210-0
It's pretty simple. I bolted mine to the frame and used a ring terminal and star washer to tie the negative wire back to the case/frame and then a hot wire up to the ignition. Fuse it accordingly. I had the body off mine when I did the physical mounting though so it was much easier. I agree with other comments about making sure the mechanical is really bad first though. Seems like AMC's liked to eat fuel pumps even back 20+ years ago when I built my 5. Which is ready to be rebuilt again.
PS those side pipes look cool but you're gonna regret them. Ask me how I know. 
Could a bad fuel pump gasket cause a no start?
SKJSS (formerly Klayfish) said:
Could a bad fuel pump gasket cause a no start?
Any leak in the system can cause it to lose prime and no fuel flows to where it needs to go. It's an odd one, but yes. Some older cars had glass fuel filters. If the cork got dry, it would cause the system to lose prie, and no start. Fuel is not getting to the carb, you just need to see where it's stopping. Start at the pump and go forward from there.
SKJSS (formerly Klayfish) said:
Never messed with a mechanical pump before. Is conversion to electric as simple as putting one in the line near the tank and then leaving the old mechanical one in place?
Here's the Jeep, the price is after all the fees
https://www.mecum.com/lots/1101601/1976-jeep-cj-7/?aa_id=534210-0
Don't do it. (My worthless opinion.) Replace the pump if it is bad. And yes, you can bench test a mechanical fuel pump. You need a vacuum/pressure gauge with appropriate attachments and a vise to mount one of the pump ears in to hold it.
Wow. Ignore my previous advice. There's not much left from '76 on that. Maybe the frame and axles. Should be a rocket when it runs right!
That fuel pump was only used on 1969 AMC cars, according to Carter. There was no 360 in 1969. You have a mystery to solve if you need to replace it. The displacement is cast into the block by the motor mounts, both sides.
I don't recall if you said which carb it has but if it's the ubiquitous 2 barrel Motorcraft most AMC V8s had, the lid unscrews quite easily revealing the float and its bowl. And it'll fun fine on level ground with the lid removed. What you could do is fill the bowl with a small bottle, start it, and watch to see if it maintains level in the float bowl. Be careful no to tear the intricate little gasket that sits between the lid and the carb body.
Yeah, not a ton left from '76. I can only guess how much horsepower it makes. I'm snowbirding in Central Florida for the winter, so I have a very limited tool supply with me. Like Steve Jones said, I will just start at the pump and see where the fuel flow stops.
SKJSS (formerly Klayfish) said:
Yeah, not a ton left from '76. I can only guess how much horsepower it makes. I'm snowbirding in Central Florida for the winter, so I have a very limited tool supply with me. Like Steve Jones said, I will just start at the pump and see where the fuel flow stops.
I assume a 7 drives quite a bit better than a 5. In my experience an early V8 "5" with the narrow track ('72 - '75) was borderline overpowered with the 140 hp 304. Especially true with the 3.73 gears they came with. They just don't weigh anything and the chassis was virtually unchanged since WW2. Like I said, Stay Safe!
SKJSS (formerly Klayfish) said:
Could a bad fuel pump gasket cause a no start?
A bad gasket in the pump itself, yes. The pump-to-block gasket just keeps oil inside the engine.
Mechanical fuel pumps are temperamental. I had one in a 66 Bonneville that worked up through at least 1996. The first time it got dry, it was toast. The diaphragms seem to stay pliable in liquid gas, but if it sits a while and gets dry, you can almost count the days until it dies.
Having said that, yours looks remarkably new... which doesn't mean it's good. You can test it like people have said. It's not a speed thing, it's just a motion thing. It's a simple diaphragm and two one-way valves, much like your heart or an air compressor. The arm pulls the diaphragm which allows stuff in the inlet side. As the arm releases, the one-way valve on the inlet closes and it pushes past the outlet side valve. Dirt simple. If you chuck it up in a vise, put your finger over the inlet, and push down (hard) on the arm, you should feel suction.
You'll also find that old mechanical fuel pumps are not that special. They're more like thermostat necks, or brake pads. One part number might fit dozens of applications. Every small block chevy that rolled off the assembly line can use one fuel pump part number. There are different numbers and different pumps based on performance or application. GM did a thing where they added a return line on A/C cars to keep cool fuel flowing. They did a higher volume pump on some Corvettes, and some 2nd-gen Camaro/Firebird got a shorter fuel pump to clear the crossmember. We once got a Ford 302 running on a Mopar LA block pump. It didn't last long because the stroke the Ford was giving it was a little too long and it broke the fulcrum pin, but it worked long enough to get it home.
I don't have a vice here. I put the inlet hose back on and tried cranking it. No fuel came out, even when I moved the arm. I removed the hose and held it in my hand, put my finger over the inlet, cranked the pump and felt nothing. Do I need to remove all of these screws and look inside to see if something is broken?
