engine and drivetrain Will Not Start When Hot!!

[airborne85]

Bro,

 

you started this frenzy......with the good folks of FAQ trying to solve your dilemma, at a minimum we/I respectfully deserve the results.....

 

Again just  out of excitement I'm wondering if it was carbs or points or.......

 

ira

[bmdubl02]

My guess is that it's a grounding problem. The fact that it fires quickly when pushed points in that direction.

I had the same problem a few years ago.

[Hans]

I'd expect ignition problems to be more obvious during cold starts, so I'd be looking elsewhere first. The condition of battery cable, connections, and related bits could also be a factor, but more because there is some other problem which requires a long crank to overcome. Again, you'd sort of expect that to cause cold start problems too. 

 

I'm not familiar with the Weber hot start problem that Mike mentions, but normally the mind would turn to heat related issues, such as gas evaporating in the bowl of an overheated carb, or in the fuel filter (because it's too close to the engine), or perhaps the carb to manifold gasket. Does it smell likes its flooded? What's the choke doing when you're trying a hot start?

[chadley]

Coupla more thoughts:

 

 

• Next time you have a hot hard start condition, pull the output fuel line off the fuel pump (presuming you still have a mechanical pump) and have someone crank the engine while you catch the gas in a jar or can.  If the engine cranks for more than a few seconds with no fuel spurting from the pump, I'd suspect either an air leak in the upstream fuel line, or vapor lock. Check the fuel line routing between the firewall and pump; if it's touching the cyl head or manifold, re-route it so that it's not touching anything, and/or insulate it.  That will prevent fuel from boiling in the line when the car is sitting after being driven.  A mechanical pump won't pump vapor, only liquid.  

Check the above plus the previously mentioned ignition items and that should solve your problem.  Let us know whatcha find.

 

cheers

mike

 

Follow this advice but keep in mind that the fuel pump itself could be the culprit- the diaphragm inside can have issues until it cools off (that was my experience anyway).  $89 well spent dollars later no more hot start issues.

[knoxgeeks]

*Sorry in advance for hijacking this thread*

Sounds similar to what I've been experiencing lately, though mine will start just fine when hot, she dies after takeoff and refuses to restart unless I mash the pedall to the floor and keep cranking.

I'm running a weber, pertronix ignition, and a mechanical fuel pump.

My first inclination is that it is vapor lock, but then I thought about mechanical pump inefficiency, or that the system is sucking air somewhere.

I don't have a phenolic spacer, would this make a bit of difference at all?

[PaulTWinterton]

+1 points and get a minor tune up.

[jdt10768]

I had this problem last year, and wound up replacing my (mechanical) fuel pump. Stopped to get gas, and car would not start back up. Mike Pugh saved my ass and brought me a spare when I was stranded outside Raleigh NC. Also - Change out the fuel filter/filters, and check the screen filter on the end of the uptake in your gas tank. It may be completely gunked up with muck and filth / rust particles

[knoxgeeks]

Thanks! New fuel filter (changed twice in the past 6 months actually) after removing the tank and having it boiled/re-sealed. I noticed that the studs that attache the carb to the manifold are a wee bit long, so I'm guessing the spacer was forgotten about, or possibly removed at some point. I've made sure the fuel lines are away from any potentiall hot areas too.

Two other things that come to mind:

1.) Would a bad seal around the sending unit in the tank cause issues?

2.) This car still has the factory plastic fuel line from the tank to the firewall, from the firewall to the carb is newer, rubber fuel line. Anyone have issues with the plastic stuff? I'm thinking maybe there could be cracks somewhere and it is pulling air into the line.

3.) (sorry for the noob sounding question) How full of fuel should the fuel filter be at idle? I have a clear filter in line before the carb, and it doesn't seem to be any more than a quarter full, ever, even at WOT.

[jdt10768]

That ring gasket can cause problems I've heard. And you need the correct replacement.

 

You can buy that plastic fuel line from Blunt. If there were a crack, you would smell gas in the cabin - strong gas odor,

 

I have 2 filters in line: 1 before the pump, and one between the pump and carb. The first filter is usually full, and the second is not full. While idling, I can see gas pumping into the 2nd filter. May not be the best setup,

any comments welcome!

['76mintgrün'02]

There is apparently a plastic sleeve pushed onto the metal line coming out of the tank.  I have read that this can crack and allow air to be sucked in.  If the flexible lines in the trunk are cloth covered, they are likely original and can have cracks hidden by the cloth.  It is a good idea to replace them with new.  The plastic fuel lines seem tough.  I doubt it has cracked.  As stated above, you would probably smell gas. 

 

I would not worry too much about the level of fuel in the filter... mine varies.  I do not have the phenolic spacer and do not have your problem.  I have had a problem with a VW flooding when warm and had a friend explain that even though it seems counter intuitive to put your foot to the floor while starting, this actually opens the butterflies and lets more air in.  Is your choke opening properly?  

 

Have you checked the little filter in the Weber where the fuel line comes in?

 

My Weber 32-36 had a linkage issue which allowed the fast idling control rod (#55 in diagram) to rotate before pushing up.  I fixed it by making a brass "washer" to take up the slop.  Watch the linkage on the back of the carb when you step on the gas and see if the vertical rod rotates before pushing.  If it does, I will dig up some photos of that fix.  It resolved my slow to start warm issues.

 

here is the exploded diagram for the 32-36 

 

http://www.thelolaregistry.com/DIY/Weber%20Pics/Untitled-1.jpg

 

Tom

[knoxgeeks]

So, it was about 90 degrees here today, and I drove for awhile. I parked her at the office, got back in 45 minutes later, and she started right up, but then died within 30 seconds, and no amount of coaxing would get the engine to fire. I'm beginning to suspect the fuel pump diaphragm is the culprit, though we will see when I go back in the morning and try to start her.

[knoxgeeks]

@tom, which part is the inlet filter in the weber?

['76mintgrün'02]

part # 11 on that link.

 

here is the parts list to go with the image

 

http://www.thelolaregistry.com/DIY/Weber%20Pics/weber_parts_list.jpg

[knoxgeeks]

Thanks again. As predicted, she started with nary a hitch this morning. I'm beginning to suspect the "new" mechanical fuel pump has issues. Anyone know of a rebuild kit available for these? I looked on fleabay with little success.

['76mintgrün'02]

If it is the type with a top that screws on, they can be rebuilt.  For that matter, you should be able to disassemble and inspect it.  If it looks okay, you should be able to put it back together... it seems.  I hear the diaphram is the the same as air cooled VWs... which also had crimped pumps as well as serviceable units.  Have you disconnected the hose coming out of it and put it in a "jar" and tried cranking to see if it is pumping?  Carefully, of course.  Have you looked at the choke's butterflies to see that they are open once warm?

 

Remember what the wise ones say, "90% of your fuel problems are electrical" are you sure you are getting a spark when it is hot?  Are you running points/condenser?  I have heard of condensers not working once hot, as well as coils... I have heard such things.