Has anyone ever known of a diesel to vapor lock?

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Bret4207

Well-known Member

• Jun 19, 2020

• #1

As the title states, has anyone ever known of a diesel to vapor lock? Had a case the other day that mimicked a gas engine vapor locking 100%. I've never heard of it before, but it seems the most likely cause. Thoughts?

 

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Case Nutty 1660

Well-known Member

• Jun 19, 2020

• #1

Nope,, not possible to do it,, sounds like you have air in the system/plugged fuel filter or supply line or injection pump issues coming,, also have seen electric fuel shut offs give no fuel/low fuel supply conditions

 

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David G

Well-known Member

• Jun 19, 2020

• #1

Possible, but highly unlikely.

 

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jacksun65

Well-known Member

• Jun 19, 2020

• #1

more likely air getting into the system, loose fitting bad rubber line.

 

Janicholson

Well-known Member

• Jun 19, 2020

• #1

Vapor pressure of diesel (the tendency to be is a gaseous state at a standard temperature of 20 degrees C) is about a factor of ten lower than gasoline.
I say about, because both diesel and gasoline vary from summer to winter in the amount of volatiles (easily evaporated aromatic compounds) blended into
the fuel. This information was gathered from several sources on the net, and all were consistent in approximate relationships between diesel and
gasoline. Jim

 

Blackhole49

Well-known Member

Location

White Lake MI

• Jun 19, 2020

• #1

All vapor lock is is lack of fuel caused by engine heat. Any lack of fuel situation mimics "vapor lock". I agree
with Case Nutty.

 

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David G

Well-known Member

• Jun 19, 2020

• #1

Vapor lock "could" happen on the suction side of the lift pump. It is not possible in a pressurized system regardless of fuel, as the fuel will condense once pressure comes up.

 

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Bill VA

Well-known Member

• Jun 19, 2020

• #1

My thought is not so much vapor lock, but fuel starvation from a fuel cap that is not venting.

 

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Billy Shafer

Well-known Member

• Jun 19, 2020

• #1

Make sure the return line. To the tank is not stopped up. If it is fuel will back up and shut down the system. I have seen that problem many times.

 

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buzzinduzzin

Member

Location

se illinois

• Jun 19, 2020

• #1

try running cold water on the injection pump when it does that. If that fixes it you pump is wore

 

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Dieseltech

Well-known Member

Location

Akron, Indiana

• Jun 19, 2020

• #1

Need to know more info, what engine/injection pump to get a good answer. Diesels don't vapor lock, but if the tank vent is plugged no air in means no fuel out. If pump is rotary might be a severely worn hydraulic head, that will cause hard or no start when hot trouble..

 

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David G

Well-known Member

• Jun 19, 2020

• #1

You want to be REAL careful with the cold water. Cool the pump down with the tractor not turning, then allow the cool case to cool the rotor down. You can seize up a pump if you cool the housing and the rotor is still expanded due to heat.

 

showcrop

Well-known Member

• Jun 19, 2020

• #1

As buzzindoz. said pouring water on it will tell you if the pump simply has too much wear. I had this situation a few years back, I carried a gallon milk jug full of AMBIENT temperature water in it for if I needed to shut it off and restart. More recently I had a situation with a hard start where I simply put a wrench to a bunch of connection fittings and that cured it.

 

guido

Well-known Member

• Jun 19, 2020

• #1

Hello Bret 4207,

No such thing! Lack of fuel is more likely the cause. Usually the fuel pressure goes down to a point that it starves the injector lines. Then air enterers the system and the engine stops running, and it won't restart,

Guido.

 

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Steve@Advance

Well-known Member

• Jun 19, 2020

• #1

I guess it would be possible but would take extraordinary conditions.

A supply line run too close to the exhaust, or a restricted filter causing vacuum on the line between the filter and the lift pump, or a combination of the 2 factors.

 

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john in la

Well-known Member

Location

What part of in La do you not understand

• Jun 19, 2020

• #1

If you truly have a vapor spot in your diesel suction
side it is caused by a leak and the pump sucking air.

 

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MARK ROBKE

Well-known Member

• Jun 19, 2020

• #1

I agree with diesel tech-worn pump. I have seen a hot engine not start and it was the
pump. Mark.

 

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OP

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Bret4207

Well-known Member

• Jun 20, 2020

• #1

Well, you've all given me ideas to look into. I picked up filters and will check fittings. I was pumping the fuel pump and could hear the fuel bypassing back into the tank. The cap doesn't seal tight enough to cause a vacuum. Maybe it was just a freak thing that will never happen again.

 

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Bruce(OR)

Well-known Member

• Jun 26, 2020

• #1

I have a diesel that try's the same trick. It was suggested a plugged or obstructed tank vent. It was further suggested to run with the gas
cal loose. I backed the cap off a few turns and no more problem. Someday I might locate/repair the vent hose.