M37 hard start when warm

[Cav Trooper]

I have a problem with my 54 M37 starting after sitting 1/2 hour or so. It appears that the carb floods out. I don't know whether it is perculating. I have an electric fuel pump which I relocated from the engine compartment to near the fuel tank. I installed a marine water/fuel spin on filter before the pump. I tried to start the truck after that and it would not run. I checked the fuel delivery and it seemed I had plenty of fuel being pumped. I ordered a rebuilt carb from Midwest and the engine fired right up. It idles a little high, I need to tweek that. It drives and accelerates and idles fine other than a little high. My big problem is it will not start when hot if let set for more than 15 min. I can smell gas and if I hold the throttle to the floor it will start. The longer I let it sit, the harder it is to start if the engine is still hot. Today, it took me 45 min. of letting it sit and trying to start periodically. When it started it sputtered and blew some black smoke and finally idled ok. I drove it about 1 mile and stopped again for 1/2 hour. It started right away since I held the peddle to the floor. I got stopped at a train crossing for 10 min. at idle. I drove about 4 miles and it stalled at a red light and it took me another hour to get it started, I contribute this to vapor lock since the temp is about 90 deg. The engine does not overheat and the temp gauge rides at about 165 deg. I had another stop for 45 min. and had the same hard start problem, another 10/15 min of cranking and finally firing eradically and finally smoothing out. When I am driving, it runs great. Is there a cure? Can I wrap the fuel line without it looking like some cobbled up mess?

[Cav Trooper]

I also removed the manifolds and installed new gaskets and rebuilt the heat riser valve and set it to summer.

[Kaiser2boy]

Sounds like too much fuel. Have you tried driving it for a few miles and stop and pull out one spark plug to see if it the plugs are black and sooty from too much fuel?
I know it is a bit of work but checking the float level may be in order. Or the electric pump is over riding the float valve. I think the fuel pressure should only be around 1.5 or 2 pounds. You may need a pressure regulator after the pump.

[Cav Trooper]

I've been checking into it. I moved the fuel pump to the rear and placed the filter before the pump. I did not check the pressure of the pump. Today, I checked the pump and searched the internet and found the mfg. I called them and it turns out that pump puts out 5.5 to 9 lbs. The tech said the filter should be on the out put side of the pump and I can regulate it down to 4-5 lbs. I ordered a fuel regulator and will replumb the filter when the reg arrives. I'll go from there.

Thanks

[Kaiser2boy]

OK but 4 or 5 pounds is still about 3 times what it should be.
I had to dig around and get a regulator that knocked mine down to like 3 pounds when I was on an electric pump. I got one at Auto Zone , had to order it but it worked.
I have to check again on what the factory pump puts out but it is not much at all. I still think 5 pounds is on the high side.

[Cav Trooper]

The problem is finding a 24vdc pump that only puts out 2-3 lbs. The factory tech didn't have a problem with regulating down to 4, the reg. I ordered will go down to 1. I'll have to dig up the spec on the mechanical pump and see what it is rated at.

[Kaiser2boy]

I cheated with my electric pump. I ran a line from the inner conector cable between the batterys to get 12 volts and ran it through a isolation switch to a 12 volt pump.
I had the engine totally rebuilt last year. The rebuilder rebuilt everything on the engine , everything. So it is as it was when new so I am not running an electric pump now.

[Cheyenne Dave]

There are in-line pressure regulators available from NAPA and other sources. Very easy to install and adjust...

C.D.

[Cav Trooper]

I found a regulator on ebay with a gauge. Should be here today. I checked the floats, they were wrong but, they were set a about 1/4 in. so they were low. I also found a cracked fuel line coupling over on the left side of the truck. All lines had been replaced with new from the PO so, it looks like they over tightened one and split it. I fixed that. I installed new bushings in the distributor and a electronic module. Now I'm off today to get a safety switch to install in the oil line for the electric fuel pump. Also, the fuel pump mfg. tech told me I need to switch the filter placement to the outlet side of the pump. Once the reg. gets here I'll do all of that and hopefully it's done. I am also getting a new piece of tubing and fabricating a new line that puts it further away from the manifold. I am planning on taking the truck to the MVPA convention next month so, I need to get all of this stuff done so I don't get stranded along the road if possible. I'm only about 35 miles from Dayton, not too bad a drive and I can get there by country roads. Thanks for all the help.

[Charles Talbert]

OK but 4 or 5 pounds is still about 3 times what it should be.
I had to dig around and get a regulator that knocked mine down to like 3 pounds when I was on an electric pump. I got one at Auto Zone , had to order it but it worked.
I have to check again on what the factory pump puts out but it is not much at all. I still think 5 pounds is on the high side.

The correct pressure is 4-5.5 psi; when installing an electric pump, we go for 4 psi; never had issue with that.

[Kaiser2boy]

You are absolutly right with the 4/5 pounds. In my fuzzy mind I just remembered the electric pump that "WAS" on mine pumped out way more than it should and it was a bit of a chalange finding a regulator to knock it down to 4 or 5 psi. The pump that was on mine kicked out around 15 psi, a little high. As you know I am running on the original mechanical pump now.

[Cav Trooper]

Most of the problem solved?????

Ok, I've been working on this problem and I think I have most of it fixed. I installed a pressure regulator in the line and set it at 4psi. I rerouted an new fuel line out as far as I could to help prevent vapor lock. I checked the floats and they were actually low, I readjusted to spec. I found a fuel line coupling leaking and replaced that. I replumbed the fuel filter to be on the pressure side of the fuel pump. I also found a bad electrical connection to the fuel pump. I have since driven the truck about 150 miles and the only thing that still happens is that after stopping and shutting the truck off for a 20 to 30 min. it is hard to start ie; acts like it is flooded. If I start it as if it is flooded/pedal to the floor, it will start right up, if I don't floor it, it will act flooded and not start. I can deal with that as long as I know what to do each time. I drove 48 miles one way up to the Dayton MVPA show this last week and it ran great all the way. I took back roads and it was about 1 1/2 hr. drive at 35 to 50 mph. I had no vapor lock issues and the temp was around 90 deg. I think the problem is solved, at least for now. I also installed a electronic ignition module, don't know if it helps or not but the truck fires right up. I got 9mpg for the whole trip.

[Kaiser2boy]

It always amuses me how older gas engines that are made exactly the same each have some little quirks that make each one have its own little tricks to start and run right.
Once you have found your engines "personality" and also the trucks peronality you and it will get along way better.
9 MPG Wow was the trip down hill both ways? snicker.
I have found that the only way I can fill the gas tank all the way is to make sure the engine is shut off. Another snicker.
The thing is not good on gas however it has a 20 star crash rating Ha Ha Ha..

[Cav Trooper]

You are right on, I started driving at 16 and my first car was a 50 chevy for $30. I've had over 50 cars and everyone is different.

[gusbratz]

mine is the same way, pedal to the floor and crank for 30 sec before it starts. sucks because i use mine for hauling dirt and fire wood so it gets started and stoped a lot. let me know if you figure it out because i would like to know. by the way. the 12v pump hooked up to 1 battery makes it unbalanced and will wear out the batteries. i know from expierence.