That's what I would try first.
CK5
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Vapor lock
- Thread starter 76k5blazerr
- Start date
And install an electric pump directly under the tank. Your problem is the fuel is boiling between the pump and the tank, with that line getting warm and running under vacuum it will boil easily. If there are any restrictions in the fuel system the problem gets worse.
Did you check the sock inside the tank??
I say that you have a bad pump.
My '72 C10 has a blazer tank in the tail of the frame, feeds a 406 to the 5200 rev limit. Only the mechanical pump.
My Dad's ( now my son's ) '72 had a 3 tank setup with no electric pump feeding a 400.
Dad's truck got headers in 1973. It had about 300 on it when we tore it down for a build.
I've had headers on a couple of C10 trucks since '86. (?)
Dad's '69 396 C10 ,only the mechanical pump.
I would still leave the spacer, but that's just me.
Check to make sure that it isn't sucking crap into the pump too.
Please don't think that I am trying to be a d**k.
My '72 C10 has a blazer tank in the tail of the frame, feeds a 406 to the 5200 rev limit. Only the mechanical pump.
My Dad's ( now my son's ) '72 had a 3 tank setup with no electric pump feeding a 400.
Dad's truck got headers in 1973. It had about 300 on it when we tore it down for a build.
I've had headers on a couple of C10 trucks since '86. (?)
Dad's '69 396 C10 ,only the mechanical pump.
I would still leave the spacer, but that's just me.
Check to make sure that it isn't sucking crap into the pump too.
Please don't think that I am trying to be a d**k.
I appreciate the advice, you aren't coming off as a dick don't worry! So you think that even though this is a brand new fuel pump that it is the problem? Remember, the first time this issue happened I replaced the pump, that was my first instinct and then it did it again, so I started thinking vapor lock, now after changing all the rubber in the fuel system and the carb spacer it still does it, and now i can't even drive the truck because it will only run 5-10 mins at a time, before it dies and you have to pour gas in the carb. I am at the point where I am about to yank the seat out, pull the tank, clean it, replace the sending unit, bend up all new fuel lines, run them outside the frame, away from any and all heat and put another return line up by the carb from a dual outlet filter. What do you say?
Well since you reminded me of the first pump swap, it may be the pump getting contamination in it messing with the valves, but that could still mean another swap.
I just don't see how you are still having problems unless it's a bad pump or contamination of the pump. I mean with all that you have done, what else is left?
Maybe you are onto something about cleaning the tank, but I personally would try changing the pump again and put a filter right before the pump. Preferably one of those cheap, plastic see through ones. But you would have to purge the air out of the line and filter. Then you should have a way to see if it is junk screwing with you, or its pulling vapors.
Yes, you could install an electric one under the cab, but be careful with the pressure.
And I would try to decide if heat from the exhaust or possible gravel from the front tire makes your decision on mounting inside or outside the frame.
Too bad that I couldn't have given you the tank out of my son's truck, it was really clean.
I just don't see how you are still having problems unless it's a bad pump or contamination of the pump. I mean with all that you have done, what else is left?
Maybe you are onto something about cleaning the tank, but I personally would try changing the pump again and put a filter right before the pump. Preferably one of those cheap, plastic see through ones. But you would have to purge the air out of the line and filter. Then you should have a way to see if it is junk screwing with you, or its pulling vapors.
Yes, you could install an electric one under the cab, but be careful with the pressure.
And I would try to decide if heat from the exhaust or possible gravel from the front tire makes your decision on mounting inside or outside the frame.
Too bad that I couldn't have given you the tank out of my son's truck, it was really clean.
Well, I'll tell you what I haven't done, and that is pull the sending unit and check it, and the sock. BUT, I have a fuel filter on top of my tank filtering the fuel right before it hits the start of the fuel lines, as well as a filter by the carb. So I am thinking that there is no way crap is getting in my fuel pump unless the lines between the first filter and the pump are crusty inside, but they look fine on the outside. I don't know, I'm stumped at this point. If I did the filter before the pump as you were saying was do I need to do to purge the air out? Also, what is a good way to isolate exactly where they vapor lock is happening? Is there a way?
Did I miss that you have the filter at the tank? That should catch any crap!
But I would wonder if that could be a part of the problem since it is at the top of the siphon tube for the feed line. If there is air in the filter, or a tiny leak in a connection, that could contribute to not enough gas flow to the pump.
Think of when you siphon water from a bucket, it needs the air out of the line to flow well.
I would try to look inside the feed line to try and see if it has rust or junk in it. But that is hard to see, of course.
To purge the air from a filter down in front of the pump, you would need to have it vertical with a good flow of gas. You could use longer pieces of hose to do it by letting the engine run while you move the filter. But then you would want some way to hold the filter while driving to test it.
Try taking the one out at the top of the tank and try again. That's easy to try.
I'm crossing my fingers for you!
But I would wonder if that could be a part of the problem since it is at the top of the siphon tube for the feed line. If there is air in the filter, or a tiny leak in a connection, that could contribute to not enough gas flow to the pump.
Think of when you siphon water from a bucket, it needs the air out of the line to flow well.
I would try to look inside the feed line to try and see if it has rust or junk in it. But that is hard to see, of course.
To purge the air from a filter down in front of the pump, you would need to have it vertical with a good flow of gas. You could use longer pieces of hose to do it by letting the engine run while you move the filter. But then you would want some way to hold the filter while driving to test it.
Try taking the one out at the top of the tank and try again. That's easy to try.
I'm crossing my fingers for you!
Just a thought, I didn't read back but did you remove/change the paper filter in the inlet if the carb?
No I haven't.
Might or might not be there but worth checking.
Well Guys, it wasn't vapor lock. Pulled the seat out of the truck today and pulled off the fuel filter that was on top of the tank it was absolutely done for, full of gunk, then I replaced the fuel filter and took the truck for a drive and it never died on me. Got home, after my 10 minute drive there was already crap in the filter, pulled the sending unit, wow, it looks like it's original to the truck. Then I pulled the tank and a whole lot of rust and shit came out. So, I've found my problem. Now, do you guys think the tank can be cleaned or should I replace it. If it can be cleaned that is the route I will go because new tanks are like 150-200 bucks. What do you guys think?
Glad you figured it out!
I know you can clean it, but the cost might start approaching the replacement cost. If you can swing it, I'd go new.
I know you can clean it, but the cost might start approaching the replacement cost. If you can swing it, I'd go new.
How would I go about cleaning it?
I have no personal experience, but I believe that Eastwood sells stuff for this problem. I have had good results from the few things that I have purchased from them, not necessarily cheap stuff.
There cheap enough, replace it funds permitting of course.
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Just to clean it? Dump out the gas, shake it around, dump it, repeat several times. Then drop some small chunks of something into it shake it,dump it, rinse it with water between dumps, repeat, rinse it out, look in with a flashlight. repeat if necessary. Then when it's got no more loose crap in it swish a little gas in it to get the water out, maybe repeat. then put it back in, and install new filter where it is easy to change. It will be much cleaner and buy you some time. Mind you this is the cheapest way to do it but it will help
I'm liking this idea, you guys ever tried vinegar in a gas tank? Like as if you were cleaning a radiator out? I'll also try to find some small rocks or marbles to shake around in it.
ekajkrats
1/2 ton status
Don't guys use heavy chain link sometimes to clean 'em out? I imagine you can get a short amount for cheap from a hardware store if you dont have any lying around. I have no experience with this as I went the new route because mine was dented in big time.
-Jacob
-Jacob
yeah, chain / rocks / golf balls / whatever you have laying around that will beat the inside of the tank. Make sure you count the quantity lol
don't know much about vinegar, might be more of a radiator fluid / rust thing but for a gas tank........ gas is pretty good at cleaning stuff
don't know much about vinegar, might be more of a radiator fluid / rust thing but for a gas tank........ gas is pretty good at cleaning stuff
I decided to just order a new tank, mine is pretty rusty and has jb weld patches on it. Don't want to have any more problems with fuel, so i splurged.
