Hard start after two days.

Luckymac · Aug 13, 2018

Some time age (maybe a year, maybe more) there were a few threads about long cranking times after the Jeep sat for a few days. This seemed to be limited to carbureted YJs. At that time we thought the problem could be due to a missing one way valve between the fuel filter and the return line. I bought an aftermarket one way valve and that seemed to work for a time but the situation was never fully resolved. I learned to live with the problem, just considering it a minor quirk of the carbureted YJ.

Fast forward to two days ago. I replaced my rear main seal and power washed my motor. I was sure I'd cured all the oil leaks.
I parked the Jeep in the garage and found the fuel pump was leaking oil. I bought a new gasket and a tiny tube of gasket maker. It seemed simple enough to put a new gasket on the fuel pump.

NOW, here's the question! When I disconnected the line that runs from the top of the fuel pump to the carburetor, no gas ran out. The line runs straight up from the top of the fuel pump for about 14 inches and runs over the valve cover to the carb.
I would expect there to be gasoline in the line. All that I can think of is that there might be a hole in the FP diaphragm allowing gas to run backwards over the course of a few days and dilute my motor oil.
With the fuel pump having to fill about two feet of fuel line, no wonder the Jeep cranks for a bit before starting after it sits for a couple or few days.

A new fuel pump is $22.00, so that's not the issue. I'm going to buy and install a new pump. What I'm asking, has anyone else ever noticed that when disconnecting the steel fuel pump to carb line that no gas ran out?

If anyone out there is experiencing long cranking times after their Jeep sits for a couple days, please disconnect the fuel line at the top of the fuel pump and note if any gas runs out.
I'll keep the forum advised if a new fuel pump solves the mystery.

Good Luck, L.M.

Luckymac · Aug 14, 2018

New fuel pump is in and Jeep runs just like always, but no oil drips.

Now the trick is to not use the Jeep for three days to see if the new fuel pump cured the long cranking issue.

Good Luck, L.M.

Instructor9 · Aug 14, 2018

Have exactly the same problem.
Just pulled mine.
No gas.
I replaced the fuel pump last summer and noticed no difference.
Just like you, i chaulked it up to a carburetor/Jeep thing.
Since buying my old Camry (for those rainy or hot days, mine sits some. Sometimes I hit the pedal, crank for 5 seconds. Nothing. Crank a little more and usually it fires off. Sometimes if it sits for a week or so, I’ll have to hit the pedal twice (once, crank for 5, crank for 5 more, stop. Hit the pedal again begin cranking sequence again. It always fires eventually so I’m okay with it.
When it was my DD I didn’t have that problem.
If I hit the pedal once and get it cranked, I won’t have to touch the pedal again the rest of the day to crank it.
It’s still running the carter.
Sent from my iPhone using Tapatalk

Luckymac · Aug 14, 2018

Instructor9, thanks for checking.

I cleaned the old fuel pump and put it back in the box that the new fuel pump same in.
If there's no difference, perhaps I can give it away to someone than might need it.

This episode got me thinking. Perhaps I'll put a one way valve between the fuel pump and the fuel filter. That might stop the fuel from draining back and making the fuel pump fill the carburetor feed line before the Jeep will start. It takes a couple days for the fuel to drain back and I like driving my Jeep, so it might be a while before it sits two or three days without being driven.

I'll keep the forum posted.

Good Luck, L.M.

Rudys88 · Aug 16, 2018

Its been two years now since I installed a metal check valve in my 88 yj and it has solved my hard/long start problem and has never returned. Prior to that, it took several long cranks it if sat for more than a day. Hope you figure it out and be sure to let us know.

Luckymac · Aug 16, 2018

I too, have the 6mm metal one way valve between the fuel filter and the overflow return line. It seemed to help a bit but never fully solved the issue.
I started with a plastic one that worked great for several months and then quit working. I bought a metal one, thinking the gasoline wouldn't bother it. The metal one only provided partial relief.
I've ordered an 8mm one for installation between the fuel filter and the fuel pump.
I'll keep the forum posted on my results.

Good Luck, L.M.

Rudys88 · Aug 16, 2018

Luckymac, One last thought. do you have your filter housing level and even a slight upward tilt and above and the inlet to the carb fuel inlet. I've read that the filter and line position leading to the carb could be an issue. When working on mine, I wrapped the line leading across the valve cover and then wrapped the steel fuel filter with fiberglass heat wrap thinking that the engine heat when just shut down was causing the fuel to boil and push the fuel back to the tank. Maybe this helped some but the check valve was the clincher for me. Your symptoms of an empty fuel line leading to the fuel pump is a strange one since the pump has its own check valve. I will try and check mine tomorrow and let you know.

Luckymac · Aug 16, 2018

I'll have to check the exact position and location of the fuel filter. I covered the fuel line from the fuel pump to the fuel filter in corrugated plastic conduit some time ago as insurance against vapor lock. I'll stop by the auto parts store tomorrow for heat wrap tape for the fuel filter. It can't hurt and just might help.
I feel I'm close to a resolution.

Thanks & Good Luck, L.M.

Rudys88 · Aug 16, 2018

Today i removed the fuel line from the top of the fuel pump and like yours, only a few drops of fuel came out. The jeep has been sitting for 3 or 4 days and when I parked it, temps here in Dallas were over 100. After the line goes up and over the valve cover, it dips down 3 or 4 inches then levels out and stays level all the way to the carb. With the return line on top and the filter wrapped with fiberglass heat tape, it is still holding fuel. I removed the breather and actuated the throttle and saw strong shots of fuel so I know that is fuel available. There appears to be enough fuel to get it started and then refill the line quick enough to keep it going. I suspect the engine heat when parked is vaporizing the fuel in the line enough to push some of it past the return line but still enough in the filter housing and float bowl to start it. Hope this is helpful.
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spoof145 · Aug 22, 2018

Rudys88 said:
Its been two years now since I installed a metal check valve in my 88 yj and it has solved my hard/long start problem and has never returned. Prior to that, it took several long cranks it if sat for more than a day. Hope you figure it out and be sure to let us know.

Which fuel line do you put the check valve on? The inlet before the fuel filter? or one of the other lines? I would like to know myself since i'm having this same issue, and have since I bought the jeep.

Luckymac · Aug 22, 2018

A couple years ago another poster noted that in the Factory Service Manual diagram of the fuel filter that there's a one-way valve between the fuel filter and the fuel return line.
He (and I) supposed that this one way valve got discarded on most carbureted Jeeps at some time in the past. The valve is housed within the rubber hose and if a technician didn't know to look for it, it would be easily discarded with the old hose, if a new fuel filter came with new hoses.
He discovered that the factory one way valve is no longer serviced and neither of us could find an identical aftermarket valve.
I bought a pair of universal plastic one way valves and I believe he bought a metal one.
After some time (several months or more) the hard start after a few says returned on my Jeep. I guessed it was because the gasoline had deteriorated the inside of the plastic valve. I replaced it with the second valve, but that didn't fix the problem.

Then I bought a metal one way valve and recommended the same to other posters. Still no fix.

Recently I discovered the oil leak at my fuel pump and decided to replace the gasket. When I removed the fuel line and no gas came out, I thought "It appears the gas has run back to the tank due to some fault in the current fuel pump. It must take a couple days for that to happen, because with an empty line, the engine has to crank for several seconds to fill the line and get gasoline to the carb". I decided to install a new fuel pump and see what happens.

I drove the Jeep to town on Friday after installing the new fuel pump a day or so earlier. Then I didn't drive the Jeep all weekend. On Monday afternoon, I cranked the Jeep and it fired immediately and continued to run.

So now, I have a new fuel pump and an aluminum universal one way valve between the fuel filter and the fuel return line. The Jeep fired right up after sitting from Friday afternoon to Monday afternoon.

Knowing what I know about how things go, I'm not convinced that I have the ultimate cure yet. The plastic universal one way valve seemed to cure the problem for a while, so maybe the fuel pump developed a fault that caused the symptoms to return and there was nothing wrong with the original plastic universal valve.
The Jeep is my go-to ride, but I'm retired and don't drive every day. Once I allow it to sit for several days and done so several times, I'll have a better handle on if it's fixed or not.

I'll keep the forum posted.

As stated above, the one way valve goes between the return outlet of the fuel filter and the return line to the gas tank.
Pic is from a couple years ago with the plastic valve in place. I now have a metal valve and the outlet has been rotated to 12 o'clock.

Good Luck, L.M.

spoof145 · Aug 22, 2018

Thanks. I saw that on one of your older posts after I searched more, and I ordered one from Amazon, will be here in 2 days.

Luckymac · Sep 4, 2018

UPDATE....

Well, after sitting a few days I find the Jeep has to crank for a few seconds before firing.
If I drive it every day, it starts right away. Just push the gas pedal and turn the key. Starts right up.

I have the metal one way valve between the fuel filter and return line and a new fuel pump.
When I disconnected the pressure line between the fuel pump and the fuel filter, there was no fuel to drip out of the line. I reasoned that there was a bad one way valve within the fuel pump and the line was draining as the Jeep sat for a few days, so I installed a rebuilt fuel pump. That was a few weeks ago.

The Jeep is my daily driver, so it took this long for me to have the Jeep sit for three days more than once just to confirm that the one time wasn't an anomaly.

I have a slightly larger one way valve to install between the fuel pump and the line that runs up to the fuel filter. I'll keep the forum posted on my results.
BTW, the outlet on the fuel filter is at 12 o'clock.

If this is the greatest problem with my Jeep (it's not), I don't really have a problem. It's something I can live with, except my OCD won't allow me to ignore it.

Now, if I could only be able to set my clock.

Good Luck, L.M.

jeepbilt · Apr 29, 2021

Luckymac said:
UPDATE....

Well, after sitting a few days I find the Jeep has to crank for a few seconds before firing.
If I drive it every day, it starts right away. Just push the gas pedal and turn the key. Starts right up.

I have the metal one way valve between the fuel filter and return line and a new fuel pump.
When I disconnected the pressure line between the fuel pump and the fuel filter, there was no fuel to drip out of the line. I reasoned that there was a bad one way valve within the fuel pump and the line was draining as the Jeep sat for a few days, so I installed a rebuilt fuel pump. That was a few weeks ago.

The Jeep is my daily driver, so it took this long for me to have the Jeep sit for three days more than once just to confirm that the one time wasn't an anomaly.

I have a slightly larger one way valve to install between the fuel pump and the line that runs up to the fuel filter. I'll keep the forum posted on my results.
BTW, the outlet on the fuel filter is at 12 o'clock.

If this is the greatest problem with my Jeep (it's not), I don't really have a problem. It's something I can live with, except my OCD won't allow me to ignore it.

Now, if I could only be able to set my clock.

Good Luck, L.M.

Install fuel filter with the return line port at the 12:00 position.

Utse · Jun 21, 2023

I have also.
replaced fuel pump twice. Purchased new Weber carb. Still hard starts. After sitting

Got it at last · Jun 21, 2023

Welcome to the forum!

We've tried several fixes over time but nothing definitive has ever completely solved it.

Luckymac · Jun 22, 2023

Welcome to the Forum @Utse

I've tried one way valves at the fuel filter overflow and at the feed side of the fuel pump. I've installed a new fuel pump, thinking that gasoline is bleeding back to the tank. I don't remember what else I've tried.

Got it at last installed a Sniper FI setup. That cured the problem for him and it has other benefits. That sounded like a good idea, so I installed an in-tank electric fuel pump in anticipation of installing a Sniper on my new motor. The electric fuel pump puts out way more pressure than the old mechanical fuel pump so it needs a fuel pressure to work with a carb. So for now, I'm running the electric in-tank fuel pump with a regulator to my reman Carter BBD carb. That flat cured the hard start after sitting for a few days. All I do now is turn the key to "on", count to 5 and then step on the gas pedal to set the choke. When I turn the key to "start", it fires immediately.

It may be the Carter carb was leaking gas from the fuel bowl into the manifold and drawing fuel up the line between the carb and old mechanical fuel pump. The empty bowl and fuel line may be what was causing the long crank times.
Now that I have the electric fuel pump, when I turn the key to "on" and wait 5 seconds, the in-tank pump can fill the line and bowl without the engine cranking like it has to to activate a mechanical fuel pump.
If I drive the Jeep every day I don't have to wait the 5 seconds. Just tap the gas pedal and crank. The Jeep starts right away.

I wonder what the guys that are running MC2100 carbs or Weber carbs are experiencing?

Pic #1 is the fuel filter
Pic #2 is the fuel filter and regulator.
Pic #3 is the regulator connected to the carb and overflow back to the tank.

Good Luck, L.M.

Got it at last · Jun 22, 2023

Fwiw, I rarely had the problem when running an MC2100 on my 4.2's, usually just after shutting it off when hot and the float bowl would evaporate or drain out.

Luckymac said:
Got it at last installed a Sniper FI setup. That cured the problem for him and it has other benefits

I left this out earlier, Pricey but what a game changer.

Hard start after two days.

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