08-03-2019, 02:36 PM | #1 |
Nincompoop village idiot
Join Date: Apr 2018
Location: Michigan
Posts: 9,673
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Fuel pump/vapor lock?
Ok I'm not sure what else to do here... I'm a little stumped and hoping maybe one of you has run into the same thing.
I can drive thr cart, no problems at all for a good 5-6 miles. Runs great, great power no problem. After 5-6 miles it will starve for fuel. Theres no fuel flowing from the fuel pump. I've replaced all the fuel lines and filter. Replaced all the lines with the clear blue ones so I can see through/in them. Replaced fuel pump with the newer plastic style. (The original pump was doing the same thing which is why I replaced it) Replaced and verified the pickup tube is good, no air leaks or cracks. Fuel tank vents fine Pulse is good, pulse line is clear. I swapped the fuel pump with my carryall fuel pump, same thing. But in my carryall i can drive 10+ miles and it never misses a beat. If I let it sit for a half hour, it instantly primes itself when I hit the gas, then fires up and runs great. At least until it does it again. Short of installing an electric fuel pump (that may be my next step) I'm not sure what else I may be missing? |
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08-03-2019, 03:31 PM | #2 |
Getting Wild
Join Date: Mar 2018
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Posts: 80
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Re: Fuel pump/vapor lock?
That's a lot of miles. Is it getting hot; close to overheating?
The fuel pump works off vacuum from crankcase. That vacuum line can sag too much and blow-by oil or vaporized oil may restrict the vacuum. Did you also replace that vac line and position it right and with correct length. Check where that vac hose is clamped to engine. Tight? Last edited by aghead; 08-03-2019 at 03:37 PM.. Reason: more info |
08-03-2019, 03:37 PM | #3 |
Nincompoop village idiot
Join Date: Apr 2018
Location: Michigan
Posts: 9,673
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Re: Fuel pump/vapor lock?
Not overheating, no. If I manually squirt fuel in the carb, it will fire right up, no problem. But the fuel pump just stops pumping.
My carryall, same engine bigger cart can run twice the distance and not miss a beat. |
08-03-2019, 03:42 PM | #4 |
Getting Wild
Join Date: Mar 2018
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Posts: 80
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Re: Fuel pump/vapor lock?
maybe take that vac hose off at the pump, hold finger on hose while gassing the carb to make it run and see if its pulling vac. It may pull vac by just turnning over/ not running?
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08-03-2019, 03:47 PM | #5 |
Getting Wild
Join Date: Mar 2018
Location: fed witness protection
Posts: 80
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Re: Fuel pump/vapor lock?
Another issue, may be suckin trash and restricting tank pick up tube. Once sits awhile trash falls back down into tank? Maybe shut off valve issue ?
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08-03-2019, 03:51 PM | #6 |
Nincompoop village idiot
Join Date: Apr 2018
Location: Michigan
Posts: 9,673
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Re: Fuel pump/vapor lock?
No, the tank is definitely clean. I removed the tank and cleaned it really well when the cart was apart, I know for certain theres no trash in there
The pulse line going to the pump has a good strong pulse too. |
08-03-2019, 04:01 PM | #7 |
Getting Wild
Join Date: Mar 2018
Location: fed witness protection
Posts: 80
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Re: Fuel pump/vapor lock?
Once the motor stops, is there still vac to the pump?
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08-03-2019, 04:06 PM | #8 |
Nincompoop village idiot
Join Date: Apr 2018
Location: Michigan
Posts: 9,673
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Re: Fuel pump/vapor lock?
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08-03-2019, 04:55 PM | #9 |
Bonafide Nincompoop
Join Date: Dec 2015
Location: Charlottesburg Va
Posts: 8,987
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Re: Fuel pump/vapor lock?
Bowl vent on the carb is clear and the carb vent hose is not obstructed?
Run it until it stops, pull the fuel hose off the carb, stick it in a bottle, and crank the motor. Do you get fuel flow? If no, open the fuel cap on the tank, crank again. Does it flow now? If no, pull the supply hose off of the tank outlet/shut-off valve and crank again. Flow? If no, pull the pulse hose off the engine side and look for oil dripping out of the end. Crank the motor and make sure you have pulse at the outlet nipple on the front cover. Reconnect the pulse hose, pull the top end of the pulse hose off the pump, crank for 20-30 seconds and make sure pulse is steady for the whole time. Someone else posted an issue similar to this a while ago and I'm not sure if there was ever a resolution. Seems like he had tried several different pumps, new lines, hoses, filters, but was still losing pulse after running for a while. Best I could figure was some obstruction inside the crankcase blocking the pulse nipple after it had been running a while. But like I said, I don't remember ever seeing an update with the resolution. (I don't remember what I ate for lunch yesterday either so take that for what's it's worth) |
08-03-2019, 05:09 PM | #10 | |
Nincompoop village idiot
Join Date: Apr 2018
Location: Michigan
Posts: 9,673
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Re: Fuel pump/vapor lock?
Quote:
If I pull the fuel line off the carb, no flow. Opening the tank cap doesnt make a difference either. I've pulled the line off the tank going to the fuel pump and dropped it in a jar of gas, still no flow. No oil in the pulse line. I've got clear lines so can see that easily :) If I pull the pulse line off the fuel pump, have a good strong pulse there too. It's really odd. And 100+ degrees outside, maybe it wouldnt do it if it weren't so hot? Let it sit 15 minutes and it will immediately fill the lines and filter with gas and run like nothing ever happened. It's like the fuel pump just decides its tired and wants to take a break If I cant find anything else, I bought the fuel pump up the street at the local dealer. Monday morning I can drop in and swap it out for a new one, but I really dont know that it is bad? I'm just running out of other things to check lol |
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