Fuel Issue

my ride is a jeep 304-2.
engine seems to be starving for fuel. new mechanical fuel pump installed
last year. I have a clear plastic gas filter. the gas just trickles into the filter.
I removed the pump thinking it was bad, but I seem to think it is ok.

 

What drives the pump?

 

Do a volume test. Almost sounds like an inlet restriction.

 

The pump is driven by a cam that is on the front of the camshaft

 

Blown out the line, backwards to the tank? Or at least suck on it to see if it is free-flowing.

You didn't say if your filter is before or after the pump.

 

The little rubber hoses on top of the gas tank are often a problem. Even if the pump is ok, if the hoses have a hole, it's like sucking on a straw with a hole in it. The volume test will show that the pump is not delivering fuel. If that fails (ie no fuel), next I would put a length of fuel hose into a gas can and connect it to the pump, and re-test. Still fails, it's the pump. If ok, closely inspect the fuel lines back to the tank. If ok, you can blow backwards into the tank and hear it bubble in a quiet garage. Or, connect your Mity-Vac and see if you can pull fuel from the tank. Divide and conquer.

There is also a screen at the fuel pickup in the tank that can get clogged with sediment. Same tests apply. For either bad hoses or clogged screen, you will need to drop the tank to fix.

Year/model/equipment? It matters, and should be in every post. Do you have the TSM for your year?

 

1977 cj5 304-2. As I stated in previous post,
I had a fuel delivery problem to the fuel filter. I did check some things that were suggested by fellow members. I blew back through fuel line to the tank and heard it bubbling. checked the line for pin holes. I think the cam or something that runs the mechanical fuel pump is worn out or something happened to it. There is a wear mark on the arm of the pump. But not excessive. I was done messing around and installed an electrical fuel pump. It was rated for 4-9 psi. 5/16" line. The fuel filter is in between pump and carb, is now full of fuel when running. (Transparent Fuel filter). It will idle fine. But when I go on the road, it has no power.
Last year installed a rebuilt Motorcraft carb. New fuel filter. Points, condenser, cap, rotor, plugs.
I have checked the points, 16-18 gap. Played with timing. Tapped on the side of carb to wake up the float.
Now when I was at the parts house, I explained my issue with them and he told me its from using pump gas. Ethanol is bad for carbs. Does this theory have any thing to do with my problem?
My jeep is parked for the winter. It was running ok when I parked It. I know thats bad, but I will not drive the streets of Pennsylvaina and have the salt eat my jeep away.
Looking for some suggestions.

 

You wrote 304, not year, model or equipment. Matters.

Did you test the fuel pressure?

No power - does it bog when you increase speed, or won't run faster than idle? Does the engine rev up normally when it's standing still and you turn the throttle? Does it stay running at higher speed if you hold the throttle open?

 

I do not have a pressure gauge. but the fuel delivery is great. the filter is full and stays full. sitting still it will idle good.
The mechanical pump is rated for 7-9psi vs. electrical pump 4-9psi.. rev it up still good. once the tires hit pavement it starts to lose power. I cant go more the 20 feet in first gear and it happens. I feather the petal to get back but it cuts out and its just enough to keep it rolling.

 

Volume is one thing, static pressure is entirely another. A fuel pump should be tested for both, to their OEM specifications. And the delivery pressure can make a difference to the carb.

"Played with the timing" Bad idea, that could cause the symptoms. Timing and points need to be set, accurately, to specification. Go from there with any alteration, but know where you are starting from. Can't get lost if you stay found.

If it was running "great" last season it may indeed be ethanol complications. I would try a dose of Seafoam, for sure.

 

I've had fuel issues in the past. The biggest one I found was the fuel line return filter. Very few of those have a restriction in the return line. the original filter had one. without that the carb can be starved under load. It took me a long time to find this one.

 

Fuel pressure gauges are pretty inexpensive and well worth the investment. Can help narrow down the issue pretty quickly. Asking a parts person who’s job it is to sell parts is the wrong path to follow when trying to diagnose vehicle issues. Few are or were automotive technicians. Been dealing with this issue for 30 plus years. “But the parts guy said”. Really? Then why aren’t they helping you diagnose the problem?

 

This.

 

Mornin Boys.. I'll chime in here.. I once had a 75 CJ w/304. Mine was doing pretty much the same thing. It'd even die on small hills. After replacing the filter, fuel pump etc etc, I finally dropped the tank. Was a buncha crud in there. I removed all the old rubber lines front and rear, blew them hard lines out , replaced the sock, cleaned thenk, and .... Problem solved.

 

tank seems newer. i did blow the lines out.
i have this jeep three years now. the guy who did it( unknown) over did a great job. The vin tag says it is a 304 with a 3 speed. it has a 4 speed. Thats all good.
But how do I determine the engine size or year? Are there serial numbers on the engine?
I ask because I am having this problem with the fuel. I would like to know just for parts replacement.
This jeep could be a Frankenstein. V-8 , 304,360 or?.Drive train.
The electric fuel pump I installed, I do not like. i would like to go back to OEM mechanical pump.
I will call a jeep dealer for a pump if they have old stock. really old.

tanks
77 cj5 304-2
4-speed

 

If the engine is an AMC there will be a designation on the block that will tell you what size the engine is.

 

1977 cj5 304-2 4-speed motorcraft carb.
Still dealing with this fuel issue.
I dropped the tank today. The tank is clean as a whistle. Fuel pickup like new.
Filter was off of sending unit. But I see no problems.
Fuel gauge didnt work, so this was an opportunity to check it out.
I noticed the position of the sending unit before I pulled it out. When I pulled it, the float was pointed at a diagonal of the tank.
It seems to me it should be pointing towards the passenger side. If using a clock as a position, standing in the rear of my jeep looking forward, should it be at 3 oclock? Please let me know.
Changing all rubber lines just to be safe.
I will reinstall my tank.
I will look into a fuel pressure gauge to check my pressure. What is a good pressure?
I noticed in a parts catalogue, the fuel filter at the carburetor had three nipples. one in and two out. One will return to tank the other to carb. Is this filter needed?
Thanks

 

Good questions, I would also like to know. I am guessing the return line is so to keep the fuel circulating back to the tank so to help keep it cool, this will help prevent vapor lock issues in hot weather..

 

The Factory Service Manual (FSM) will have much of the information you need. You do have an FSM, right?

 

IIRC sender is keyed and has one way it can be installed. If you have the right parts, this should not be a puzzle. Suggest you test the sender electrically before putting it back.

The TSM has instructions for diagnosis and repair of the instruments. The '77 TSM is free to read and download on the Tom Collins site. The electrical schematic is much better quality in the paper reprint you can purchase many places. The TSM also gives the expected pressure reading for the fuel pump.

You don't need the special fuel filter. The Jeep will run if you bypass it, or replace it with a filter with two nipples. You will give up the benefit of the special filter if you delete it. The three-nipple filter is very simple in design; there is an orifice in the filter that limits the return flow. The extra nipple goes up (12 o'clock) on the outlet side.