M52 running out of "get up and go"

[sklemm]

I took my 1957 M52 Gasser on a shake-out drive today to see how all of my recent projects were working out.

Project list:
New Zenith carburetor
New fuel tank
New gas gauge
New gas gauge sender


It did not go well.

It ran well in all gears up to about 2,200 RPMs then sputters and cuts out. It returns to normal after a couple of seconds when the RPMs drops under 2,000. I never made it over 40 MPH and that was with no trailer. With a trailer I was lucky to make it to 20.

The new carburetor only has three adjustments (that I know about); the choke, the idle speed and the needle adjustment for lean/richness. I tried adjusting the mixture leaner or richer, but it made no difference.

With all that said about the carburator I was thinking that it could actually be a fuel supply issue and not a carburetor issue at all.

The previous owner had replaced the fuel pump with a aftermarket electric Facet unit (I can't find a model number anywhere on it). And added a Bendix fuel filter.

My plan is to replace the fuel filter, the fuel pump (with a Carter P4603HD) and all of the fuel lines with new 3/8" tubing.

Does anyone have any other ideas? A timing issue perhaps?

Are there other adjustments on the Zenith carb that I am overlooking?

I have only had the truck for 6 months or so and it had on old Holley carb on it that had similar performance problems. The Holley wouldn't even run well at idle. The Zenith purrs like a kitten.

 

[panzerwillie]

It sounds to me like a ignition problem, when was the last time you look at the plugs cap rotor points condenser ect, does it shoot explosions by the exhaust, usually when its a fuel problem should backfired througth the CARB, last time i had a problem like that my condenser was acting up, if the plugs are not clean it will do it also, after you fguere it out advance the timing a little makes is it run better good luck

 

[papabear]

agreed panzer

 

[sklemm]

Thanks so much for the input.

It did back-fire a little through the carb, but mostly it just hesitated.

I will check the timing and plugs before I attack the fuel system.

 

[Floridianson]

Check the dis. cap for carbon cracks? Idle miture screw is set best with a vacuum gage. Set for highest vacuum shown on gage.

 

[nk14zp]

A old timer said one time 95% of carb problems are ignition problems. Good luck.

 

[Recovry4x4]

To paraphrase a song, Get up and go musta got up and went!

 

[armytruck63]

The spark plug wires can also be on their way out. Even the shielded military wires fail eventually. A freind in San Diego had a crappy running Mighty Mite and bad sparkplug wires turned out to be the cause.

 

[sklemm]

Does anyone know if you can use a standard induction type timing light with the shielded ignition wires? or will I need an adapter?

I only have a 12 volt model so I was planning to run it off a separate power supply.

 

[G-Force]

No it won't. either pull #1 wire off and jury rig an old spark plug wire with paper clips in ends or sometimes the shielding will slide back up wire if you take the nut loose at either plug or distributor end.

 

[ken]

Is 3/8 diameter fuel line big enough for a 600 CID gas engine? Mabye it's starving for gas at higher RPM's.

 

[dfanders]

M52 Still running out of HP at 2000 RPM..

We worked on the M52 this weeked. Her is what we did:
1) Changed Fuel filter
2) Changed Distributor cap, rotor, points, condensor, spark plugs(2243's) wires.
3) adjusted timing using light on No1 wires with shielding stripped off enought to get the timing light clamp on the wire. Power is from a 12 volt batt. Adjusted it to TDC and also tried the advance mark.

We are still having the same issue.
1) Full power and RPM range(up to 2800) in 1st , 2nd gear & 3rd gear.
2) Shift into 4th normal operation up to 2000 RPM. Once at 2000 RPM you get hesitation (hesitation, missing, loss of power)and maybe a backfire from after the carb(tailpipe). If you let off the gas and bring the RPM back below 2000 RPM , no issue.
3) If in 4th and you have the hesitation, you shift into 5th, and the tach drops below 2000 RPM , the issue goes away. Once you get your tach, in 4th, back up to 2000 rpm , this issue presents again. You can get to 40 mph in 5th , which is about 2000 RPM (gas engine with splicer tranny that is driect drive) before you get your loss of power again.

Here is what the TM says on related issues:
Engine Misfires at high speeds:
1- Faulty Ignition system
2- Improper valve adjustment
3- Restricted fuel line or fuel filter
4- Defective fuel pump
5- Spark plug gap set improperly

Engine low on power:
1- Improper fuel being used
2- Clogged fuel filter
3- Air cleaner restricted

Engine Misfires at high speeds
1- spark plugs improperly set
2- Distributor breaker opening improperly
3- Defective ignition coil
4- Defective ignition wiring

Engine does not attain max Horsepower
1-pre-igntion due to defective or improper spark plugs

As stated above, we reviewd the TM and it suggested a number of issues. Igintion was the primary one when dealing with loss of issue. We replaced the above parts ,along with fuel filter. We have a 24 volt facet fuel pump. We did not instal it, and it has no model number, fo i don't know hte Flow rate of PSI on it.
Our current thinkging is that there is a timing advance issue as the engine reaches 2000 RPM, but that it only occurs in 3rd and 4th. Maybe this is becasue the tranny is putting more of a load on the engine in these gears? How does the vacum systm in this engine work for advancing the timing?


Anyone have any thoughts on where to go next? We are looking at taking it to Eastern Surplus to have a professional mechanic try and diagnose this issue.

 

[G-Force]

Try hooking up your timing light and rev the engine. See if the timing advances. If not and the distributor has a vacuum advnce on it use a vacuum pump and apply vacuum to it at idle just to see if the diaphragm is good. Also the distributor most likely has a centrifugal advance. These are weights under the plate where the points are that will advance the timing in relation to the speed the distributor is turning. This is why when you grab the rotor and twist it it will rotate slightly and then spring back when you let go. To test this disconnect the vacuum advance and rev the engine. Look at the timing marks on the damper, they should advance. Now, how much its supposed to advance you will have to find out. It is probably listed somewhere in the manual.
Also, make sure you set your timing with the vacuum advance disconnected. I hope this helps...

 

[dfanders]

Thanks for the advice. We are going to replace the entire distributor assembly with NOS from memphis. We will also check the valve clearance..as that is listed as one possibale item. I will post back after the new distributor is in.

We suspect this is a mechnical advance, not vacum..anyone know for sure??

Cheers,
David Fanders

 

[G-Force]

If it has a diaphragm on the side it is vacuum advance. chances are due to the age it probably isn't. Also, is that Zenith carb the right cabr for that engine??
It could be the carb is jetted wrong and is basically running out of fuel or leaning out once it gets to 2000 rpm.
WOW, I just realized you guys are from Joisey!!!! Me too!!! No wonder I can understand ya!!! (Probably gonna catch hell for that remark)

 

[m139h2otruck]

Had issues with the Zeinth carb on ours, the governor diaphram was split and leaked so the governor didn't work. Also, bought a "rebuilt" distributor from Memphis that had the wrong advance cam in it, so when the engine speed increased, the timing retarded!! As stated, check the advance with the light with the engine running to be sure that you are getting full advance. Correct static timing is about 5 degrees BTDC but you can increase this to at least 15 degrees and it should run good.

 

[m139h2otruck]

Also, there is no vacuum advance on the stock distributor, just the internal mechanical.

 

[dfanders]

M139H20truck...

How did you determine the distributor had the the wrong cam...other then installing it and checking the timing and senig it was off? I will check the new one agaist the old one to make sure that cam looks close?

We are also changing out the Fuel pump to a NAPA P4603HD. We will also be replacing all the fuel lines from the gas tank, to the pump , thru the filter( which is new) and to the zenith carb(which is a replacment. This way from the gas tank to the carb is new.

Cheers,
David Fanders

 

[m139h2otruck]

Truck would set and idle fine and run around the job site at low speed OK, but was way off on power going down the road. Hooked up a timing light and watched the mark as the rpm was raised. The "cam" is not the point bump cam, but rather the weight cam under the point plate the determines the advance based on rpm. The original distributor body was broken on the lower half that goes into the engine, so we just ordered the "new" unit from Memphis. Used the advance weights/cam/main shaft from the original and replaced the setup in the Memphis "rebuilt" and it worked fine. Point cam on the "rebuilt" was nowhere as good as the old original!! Have since installed an electronic update done to the other spare from the spare truck and it fired right off on the second turn when we restarted it.

 

[dfanders]

Issue Fixed !!

The issue turned out ot be.....Fuel Pump !

We installed a new 24 volt fuel pump ( i will get the napa part number and post it later) along with replacing all the fuel lines. Truck is now able to get up to max speed and RPM in 5th gear.
We are next going to test it pullnig a 10 ton tag trailer with a M2A1 WW2 halftrack. HOpe to get about 50 MPH on the flats with it.

Thanks for all the help. I had a whole distributor ready to go in , and decided to take it for a test drive after the fuel pump work. Glad i did !



Cheers,
David