engine and drivetrain No-Start When Hot/hot Start Issues

[CharlieG]

Gruppe, 

 

I'll get the basics out of the way. '76, mostly stock M10 motor, desmogged. Stock vaccuum advance dizzy, mechanical points, standard OEM-ish coil less than a year old. Stock mechanical fuel pump of indeterminate age, replaced at some point, but never by me in the ~5 years I've owned the car. Weber 38/38 downdraft carb, electric choke, new as of September 2013. 

 

Had a no-start symptom a year ago that ended up being the little grounding wire inside the dizzy on the advance plate. Cleared that up and car has run fine since then, with the only issue being if it sits for a few days. Car will take 25-30 seconds to crank, and then fire. Once started up, I can shut it off and it fires back up no issues. If I start the car every day, it's fine, minimal crank time. Let it sit a week or so, issue returns. This issue also seems to occur after I've run it for a while, park and try and start back up - aka stop in to the store for 30 minutes or so. I've also noticed on long road trips it does start to stumble a bit after a few hours of highway driving. 

 

So, on the surface I'm thinking fuel issue. 

 

Anyways, took it out this weekend from inside the garage, fired up fine, drove it around for a couple of hours, ran great. Left it parked outside overnight, came back outside the next day. Now, hot weather, ~85 degrees or so, direct sunlight ,so the car is definitely hot. Go to fire it up, and car just cranks, cranks and cranks. Nothing. Pull dizzy cap off, check grounding wire, adjust that, nothing. Play with timing a little bit, nothing. If I advance it a good bit, it tries to fire when I hold the throttle down, but won't stay running. With the engine off, I can give it gas and there's definitely fuel coming into the carb, so I'm not quite sure which way to go. 

 

So, on first guess, I'm thinking the fuel pump has finally given up the ghost. Going to go ahead and order a fresh mechanical one and all the trimmings, but just wanted to toss it out there to see if any one had any other ideas. 

 

Thanks. 

 

-Charlie

Edited June 2, 2014 by CharlieG

[jrkoupe]

Chaaaaalie........wazzup..sorry I cant help....just wanted to say hi...still have the 02....cool

Do you know the movie i was quoting ....?.....Chaaaalie...?.....Eric Roberts was in it.

[zinz]

Sounds like the typical, Weber vapor lock problem... I've run a couple cars with the Weber 32/36 in the Central Texas summer heat and they were horrible about vapor locking. 85 degrees isn't too terribly hot, so hopefully your solution will be easy.

There are several fixes listed in the threads. Try a phenolic spacer under the carb, new fuel filter, or plugging the vent to the secondary (this may only work for the 32/36..not sure about the 38/38?)

Search for Weber Vapor Lock

http://www.bmw2002faq.com/topic/128623-vapor-lock/

http://www.bmw2002faq.com/topic/85702-fuel-vapor-lock-problem-need-help/

http://www.bmw2002faq.com/topic/84478-weber-3236-calibrated-orifice/

Best of luck,

Ed

[zinz]

I think the last link is incorrect..

This one shows which hole to plug the vent to the secondary (again, this is for a 32/36, not sure if this holds true for the 38/38)

http://www.bmw2002faq.com/topic/49989-question-about-3236-jetting/

[Stevenc22]

I had this problem. Ultimately it turned out to be my choke being set incorrectly.

[Napes]

I've had some similiar problems here in So. AZ, but usually on days when the temp is over 105º.  Mine was helped by installing some Thermo-Flex Composite heat shield sleeving (I got mine from www.PegagusAutoRacing.com). I got 1" version and slit it along the one sidet to fit over the coolant hose immediately under the fuel pump.  I ran it from the intake manifold to the front end of the hose.  I also sometimes have to pour a little cool water over the fuel pump - a couple of 12 oz. bottles usually does the trick - especially after driving 60-100 miles in over 100º heat and then parking the car for 30-45 min. before attempting to restart.  Put some bottles of water in a cooler and take it with you in hot weather.

 

Bob Napier

[CharlieG]

Update: 

 

Cooler temps today, car has been sitting inside a garage for the past 24 hours. Went to crank, it struggles, with pedal fully depressed it starts to catch, starts to almost fire, but struggles and still dies. 

[Stevenc22]

Check the chock plate. Is it closed when car cold? Does it open then car hot?

[CharlieG]

Closes when cold, opens wide when gas depressed. Obviously not able to test "hot" as the car won't run. Frustratingly, it's probably the distributor acting up again. 

[Cyclone101]

I would start by grounding you plug wires to see if you have spark, and checking the level of fuel in the carb.

If you have spark, it might be too weak under compression, but the absence should indicate a dizzy problem.

[CharlieG]

There's *some* semblance of spark, as it tries to fire, kicks a few, and struggles, it'll barely kick over and keep going with the throttle fully depressed. Set to TDC, checked gap, etc. Everything seems correct. 

 

I had a similar but not quite the same issue with this dizzy in the past, grounding issues. From everything I can tell, it's an OEM '76 Vac advance unit. Going to go nuclear option and ordered a new 008 with electronic ignition from IE. 

['76mintgrün'02]

Save your old one!

 

(I am a fan of the vacuum units and just went in the opposite direction)

 

I was reading the other day about testing the coil and condenser using a heat gun, because they can both be heat sensitive.  I would suspect either, before the distributor itself...

 

Have you tried a little starting fluid to see if it makes it fire off?

 

I had problems with a brand new set of ignition wires... maybe try a spare from the coil to cap?

 

(I am just throwing stuff out there.  Ignore me if it is annoying)

[CharlieG]

Wires are <year old, starting fluid nogo, or, more realistically, same effect as just regular gas. 

 

Spec'ed out all the parts to replace the innards on the vac advance dizzy and it came out to around ~150 bucks. For that price, 180 for a brand new unit from IE seems right on the money. 

['76mintgrün'02]

I was having "missing issues" and had bought a new set of Bremi wires and figured that could not be the problem.  I was chasing my tail for some time before I figured it out.  I know it is unlikely, but because of my experience, I thought I would put it out there.

[CharlieG]

Think I've got some decent "non-burnt" (long story) spares hanging around. I'll test today.