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No start when hot...PICS UP

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mudbog42

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Ok for some reason the motor does not want to start after it has been running for a while.:angry1: It will start up right away when cold though.:D

So far I have replaced plugs, wires, cap + rotor, tested starter(passed at autozone), tested ignition control module(also passed at autozone), did a resistance check on the ignition coil and checked out good. and have tried moving the timing around.:grind: :weld:

Also it is getting spark to all 8 plugs and getting fuel so at this point I am pretty much mind boggled:dunno: :what:

Any help would be greatly appreciated:1zhelp: :1zhelp: :1zhelp:

Also it not for my K-5, but for my 51 Chevy with a 350 and a just replaced Q-jet carb
 
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Check your fuel line routing sounds like your getting vapor lock (fuel getting hot and turning to a gas). also if your running an electric fuel pump make sure its as close to the tank as possable to prevent the same problem with the pump.
 
hmm maybe taths my problem too. sorry to hijack...but mine does this wehn its warmed up, and at times it runs worse too!

what can i do? i have a manual pump...
 
tumbleweed1002 said:
Check your fuel line routing sounds like your getting vapor lock (fuel getting hot and turning to a gas). also if your running an electric fuel pump make sure its as close to the tank as possable to prevent the same problem with the pump.
Click to expand...


Its got a manual fuel pump mounted on the block and the fuel line from that goes underneath the motor and right up against the head.

What would be the best way to route this?
 
I had the same thing on the burb which is why i suggested it be checked, my fix was to run 6an braided steel fuel line to the carb and run it a little longer to keep it off the block and head,it still travels up the front of the engine and behind the alternator like stock. good luck it worked for me:D
 
it could be your starter selonids stuck ...I had the same problem, and a 35$ wrap around starter heat shield fixed the problem
GM starters and headers do not get along, my would turn and turn and not start.
 
If it's turning over, I vote for vapor lock..

is it turning over like normal, or is it turning more slowly when it's hot?
 
4by4bygod said:
If it's turning over, I vote for vapor lock..

is it turning over like normal, or is it turning more slowly when it's hot?
Click to expand...


It turns over like normal, but this now brings me to my next question, I am now experiencing a big big power loss, what should a built 350 timing be set to????
 
Base line 6-8 deg btc but there are a lot of veriabls each engine likes timing a little diffrent depends on the combo of parts i.e. cam intake carb ign syst.
 
mudbog42 said:
It turns over like normal, but this now brings me to my next question, I am now experiencing a big big power loss, what should a built 350 timing be set to????
Click to expand...


shoot, that's a question for one of the engine gurus here.. it's been so long since I've had to time an engine.. sorry..
 
Thanks for the link on timing, I am going to read through that and hopefully find a good setting

And as for vapor lock, well just got done running it around the block a few times,(after trying to reroute but it just a rubber fuel line and got very hot) shut it down and no start, touched the fuel and it was hot though I routed it not to touch the engine at all (but it is just rubber). The clear fuel filter had no fuel in it and when I tried to look at the needles spitting fuel in the carb, nothing came out but steam, so that may be my big problem
 
mudbog42 said:
Thanks for the link on timing, I am going to read through that and hopefully find a good setting

And as for vapor lock, well just got done running it around the block a few times,(after trying to reroute but it just a rubber fuel line and got very hot) shut it down and no start, touched the fuel and it was hot though I routed it not to touch the engine at all (but it is just rubber). The clear fuel filter had no fuel in it and when I tried to look at the needles spitting fuel in the carb, nothing came out but steam, so that may be my big problem
Click to expand...

Oh yeah, that's the issue all right.. where does the line go when it comes out of the pump? right up the front of the block? Is it rubber hose all the way from the pump to the carb?

what about where the line comes out of the tank.. does the exhaust come close to it back there at all?

on my camaro, I had to take some plug wire insulating wrap, and wrap a portion of the fuel line & battery cable, ( battery is in trunk ) so that the exhaust wouldn't cook anything..

can you snap a pic of your line routing in the engine bay?
 
I'll snap some pics in the morning, but yeah it is rubber all the way from the fuel pump to the carb. I'll check from the gas tank to pump in the morning also
 
Next time its hot and won't flow gas, try regular cold tap water on the fuel pump. If that works, time for a remote electric fuel pump; to get the fuel line away from the heat source.
 
Don't laugh.

Years ago, I had this problem with a Pontiac dirt track car.. Elec fuel pump helped SOME, but did not cure it.

I ended up using an old Ford power steering cooler, mounting it above the engine. Problem solved.

I have never had this problem, if I leave the OE steel line in place, just when I replace it with rubber hose? Maybe the steel line does a better job of dissipating the heat?
 
Pics

Ok heres the pics of how it was sitting





and here it is after I moved it but the line still got pretty hot




Also the fuel line from the tank to the pump is also all rubbe, and runs along the mainframe of the underbody and look to be a pretty good distance from exhaust
 
random thoughts

Thanks for the pics.. looks to me like if the whole system is rubber, you have a lot of opportunities for pinhole leaks to develop and air to get in the system.. you don't have to have a chafing situation to develop that issue.. gasoline oxygenates like MTBE & ethanol can degrade rubber slowly over time..

looking back, my first K5 ( an 1984 with a q- jet 350 ) had a fuel system that was rubber from the tank to the carb.. (I had the gas tank replaced, and the shop didn't give me the hard lines like I wanted ).. anyway, I never had vapor lock with it that way, but then I only had it for another year after the hoses were installed, and i didn't have near the amount of hose that you have... my point is, maybe the hose underneath your truck has seen better days? How long has it been on there?

thinking out loud here... maybe you have too much fuel line from the pump to the carb.. when the engine shuts down, all of that heat radiates from the manifolds & intake, so there's a lot of surface area ( the fuel line itself ) to absorb that heat.. a metal line probably would reflect the heat.. It's also possible that the loop of hose you have from the pump to the carb is introducing an air bubble in there , by virtue of the way the hose is routed.that's a long horizontal travel coming out of the pump, and the fuel could be travellling slow enough at that point where the hose isn't exactly full when it turns upwards..an in tank pump with higher fuel pressure would overcome that..anyway,I always thought that fuel line coming out of the pump should be running vertical as soon as possible..

I would try just putting short bits of rubber line at the carb and at the pump, and run metal line as close to the front of the block as possible..

also too, try running a hard line ( or shield the one you have ) from the firewall to the pump..the heat from the manifolds may be cooking the fuel there too..
 
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