tank question

[Kaegi]

why do M37s have two fuel line fittings on the fuel tank? I dont have a manual yet.

[w30bob]

K,

One is the supply to the pump, the other is the vent to the carb.

bob

[Kaegi]

wonder why they vented to the carb? already has vent through the cap??

[w30bob]

I can't talk for the B1 version, but the first series of M37s did not have vented cap. Venting of the tank was done thru the induction system for reasons regarding fording. I don't have the ORD for the B1 but they might have switched to a cap that could be vented or closed.........the others will have to chime in here. Many folks put vented caps on the the first series trucks....but they didn't come that way from the factory.

regards,
bob

[Kaegi]

ya mine is an early truck. that makes sense. can non vented caps still be found?

[ZGjethro]

My truck is a 52 model. It has the petcock on the gas tank, bed spare storage, and the vented filler tube. I was pulling the filler tube yesterday so I could drop my tank and was wondering about the redundant venting. The only thing I could think of was that the carb venting of the tank would put a vacuum pressure on the tank, exactly what is not wanted all the time.

[Kaegi]

dont think there is enough vacuum to create pressure with fuel pump creating low pressure area as fuel goes down. it draws in fresh air frim the intake elbow. vacuum is low at the elbow

[w30bob]

Hi guys,

Non vented caps can still be found......they have the star shape on the top of the cap, but I believe there is also a cap that is vented WITH the star shape....so check for a vent under the cap when you run across one. There are also non-vented caps out there that were used on the M38 I believe.

regards,
bob

[ZGjethro]

dont think there is enough vacuum to create pressure with fuel pump creating low pressure area as fuel goes down. it draws in fresh air frim the intake elbow. vacuum is low at the elbow

Probably not, but why do they have the carb vent and the filler tube vent, if only the carb vent would work?

[Kaegi]

dont think there is enough vacuum to create pressure with fuel pump creating low pressure area as fuel goes down. it draws in fresh air frim the intake elbow. vacuum is low at the elbow

Probably not, but why do they have the carb vent and the filler tube vent, if only the carb vent would work?

So when you are pouring gas in fast from a jerry can it can vent real fast. the tiny line to carb problaby wouldnt work well as a vent for filling up

[ZGjethro]

I agree. Sometimes I don't see the obvious reasons. I fixated on the engine running case and did not consider filling