Joined: Nov 16, 2021 Posts: 63 Location: NE Washington
Posted: Sun Jun 25, 2023 2:16 pm Post subject: M38A1 fuel tank question
I had my newly restored A1 out for a drive and climbing a hill, it lost power and died.
More than likely I ran out of gas. I wasn't checking the gauge since I put a couple of gallons in it not too many miles ago.
Where is the fuel line on a stock A1? Front, rear, bottom?
Does it make sense that with low fuel an incline would draw fuel away from the pickup?
Or, is there some fuel in the tank that is not considered "useable" due to line location or tank design? (like aircraft). _________________ 1955 M38A1 MD 82551
Former owner/restorer of 1977 CJ-5, stock with factory V-8.
Used as a daily driver for seven years.
Joined: Oct 02, 2014 Posts: 1916 Location: South Carolina, Dorchester County
Posted: Sun Jun 25, 2023 2:30 pm Post subject:
JBJeep wrote:
Where is the fuel line on a stock A1? Front, rear, bottom?
None of the above.
The fuel pick-up is on top of the tank.
The illustrations on pages 70 to 76 in the September 1956 edition of the ORD9 SNL G-758 for the M38A1 show the fuel system very well, including the fuel pick-up in the tank.
I'm guessing that all but maybe an inch of gas in the bottom of the tank is usable --- maybe less on a hill. There is no "reserve".
Guessing again that an inch of gas might be about 1 gallon (out of 17 gallon capacity).
The manuals are easy and free download here on this site.
You didn't say, but guess you put some gas in the tank and it started up again proving you ran it out of gas --- and it's not some other problem?
Some folks make a dip-stick out of a piece of hardwood dowel rod as a back-up fuel gauge.
Good luck! _________________ Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Joined: Nov 16, 2021 Posts: 63 Location: NE Washington
Posted: Sun Jun 25, 2023 3:53 pm Post subject:
Thanks.
Odd that the pickup would be on top, at least it would be less vulnerable to rocks and off road hazards.
Considering how much fuel I put in it last time, and the amount I have driven, it was probably just dry-ish.
One I put some fuel in, it eventually started, but it took awhile.
Anyone else ever run out of gas going up hill a few seconds after the Jeep was running perfect? _________________ 1955 M38A1 MD 82551
Former owner/restorer of 1977 CJ-5, stock with factory V-8.
Used as a daily driver for seven years.
Joined: Oct 02, 2014 Posts: 1916 Location: South Carolina, Dorchester County
Posted: Sun Jun 25, 2023 4:39 pm Post subject:
JBJeep wrote:
Odd that the pickup would be on top, at least it would be less vulnerable to rocks and off road hazards.
Not really odd at all.
Pretty sure that many modern car fuel pick-ups are from the top of the tank.
Gravity makes crud in the tank fall to the lowest point and that's probably not the best place to pull fuel from?
JBJeep wrote:
...it was probably just dry-ish.
Is that something between having fuel and not?
Not sure that's an official term used by mechanics?
I tend to think that either the carburetor gets enough fuel to run (including uphill or down) --- or it doesn't.
Glad to hear that putting gas in the tank solved the problem. _________________ Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Joined: Nov 16, 2021 Posts: 63 Location: NE Washington
Posted: Sun Jun 25, 2023 4:48 pm Post subject:
Dryishish is having enough fuel to get halfway up a busy hill, then having the engine sputter.
The fuel gauge, once in level ground, showed some gas in it.
Yes, I know better than to trust a fuel gauge in a 68 year old Jeep, but it sure seems like a case of running out of USEABLE fuel as opposed to having a dry tank.
With my antique roadster, I have run out of gas 3-4 times, with today's fuel I don't like to put a lot into my less frequently driven vehicles.
And my excuse here is I have only driven the Jeep <50 miles, so I'm still learning its consumption.
With daily drivers I always keep the tanks full, I learned my lesson flying a helicopter years ago. _________________ 1955 M38A1 MD 82551
Former owner/restorer of 1977 CJ-5, stock with factory V-8.
Used as a daily driver for seven years.
Joined: Oct 02, 2014 Posts: 1916 Location: South Carolina, Dorchester County
Posted: Sun Jun 25, 2023 5:05 pm Post subject:
JBJeep wrote:
Dryishish is having enough fuel to get halfway up a busy hill, then having the engine sputter.
With daily drivers I always keep the tanks full, I learned my lesson flying a helicopter years ago.
Yes, I can imagine that flying a helicopter with a "dry-ish" fuel tank could be a problem.
Harder to pull over to the side of the road being one.
Yes, 70 year old fuel gauges aren't especially accurate, and as already mentioned --- they don't show USEABLE fuel, just fuel.
The needle bouncing around "E" is a message.
I don't push the limit in my 2003 Tacoma that far either, for the same reason.
It could take a minute or three of cranking to re-prime the fuel lines, pump, and carb for a re-start after running them "dry-ish".
The manual says driving range is 280 miles (loaded) on the 17 gallon tank = 16 mpg. _________________ Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Joined: Nov 16, 2021 Posts: 63 Location: NE Washington
Posted: Mon Jun 26, 2023 12:28 pm Post subject:
I just put fove gallons in it and climber the hill without any problem.
So lesson learned: Not all the fuel is useable.
Spoke with the shop that restored the Jeep...it had cleaned and sealed fuel tank,new lines and filter....so there isn't any mechanical issues.I
I've now put about 12 gallons in it and it reads about 2/3 or a tank, so the gauge is reasonably accurate. Though the original gauge has rather odd gradations...the 1/4 & 3/4 markings seem misplaced. _________________ 1955 M38A1 MD 82551
Former owner/restorer of 1977 CJ-5, stock with factory V-8.
Used as a daily driver for seven years.
Bottom line here is "Running engines out of fuel causing them to quit is UNHEALTHY for the engine and should be avoided.
With top side fuel pickups a significant amount of un-useable fuel is quite common.
I see your reasoning for not filling tanks up on your collection of rarely driven vehicles but I am also well aware of the real reason for topping off tanks on often stored vehicles is to prevent the buildup of moisture collecting on the internals of the tank and plumbing causing serious corrosion issues.
As for your difficult restart, the military solved that by having Willys add a hand priming handle on the fuel pumps that belong in the A1. You pump this handle to refill the carb bowl making starting after running out of gas simple.
Finally for ease in starting after long sitting periods or severe cold weather the Army insisted on the optional dash mounted primer pump which squirts gas directly into the intake system. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Tue Jun 27, 2023 9:48 am Post subject:
The other thing is spend the extra money and DO NOT use ethanol blended gas in vehicles that sit for periods of time. Water binds to the ethanol and won’t drain out leaving water and moisture in your tank, pump, lines and carb. And as that junk dries out it leaves a nasty residue that can create tons of work and headaches to resolve.
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