Hot Start Issue, 1974 1.8L will cold start, but will not start if engine is hot. Options

[Garrettvr507]

Hi folks, I recently bought a project car this past fall and I've been tinkering away at it all winter. It has plenty of small issues but one that I feel like I've been chasing for as long as I've had it is the hot start issue. It has duel weber carbs btw. The car will crank and I'll get ignition pretty quickly when the engine is cold. If I then go for a 10-15min drive and shut it off it will not start again until the engine is cold. So far I've replaced my alternator, starter, and I just ordered a new fuel pump. My current fuel pump seems to be working fine, but it's old, and I figured why not upgrade it. I also rerouted one of my fuel lines away from the engine bay due to concerns that I might be experiencing vapor lock.

The issue continues nonetheless and I can't seem to find a solution to my problem... If anyone else has an idea of how I should proceed, I'm all ears!

[fiacra]

Here you go:

http://www.914world.com/bbs2/index.php?sho...308904&st=0

You'll find lots of information on the hot start issue. The best way to search this site is to use google. The first search term should be 914world followed by whatever string of text you want to search.

And:

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[rick 918-S]

Some will post about adding a Rube Goldberg devise like a part that belongs on a Ford. Here's where I would go first. When this happened to me I had a member here suggest the following. I call it the Ed test. Leave your cables connected. Be sure the cables and the terminals are clean. Take a good set of jumper cables and connect one end to the positive battery side and the other to the starter positive terminal. Try starting the car. I had a cable that looked OEM new that was corroded inside the sheathing causing a serious loss in voltage. I went to the Napa parts store and had new cables made for the positive, negative and new ground strap on the transaxle. Fixed the problem I was chasing for months.

[FlacaProductions]

Welcome! Yup - that's the thread for hot start mitigation.
For searching 914World, I use this bookmark:
https://cse.google.com/cse?cx=0024083458981...772:ajvfxschcgc

[Garrettvr507]

Thanks folks! I've seen this thread before, but I'm not convinced I'm experiencing a major voltage drop since my starter will crank and crank just fine. I believe this may be more of a fuel and ignition issue since it won't fire even once while I crank it.

[Superhawk996]

Check CHT for proper resistance when hot

Never mind - carbed (IMG:style_emoticons/default/chair.gif) - just learning to read (IMG:style_emoticons/default/biggrin.gif)

How do plugs look? Is it running super rich? Rich mixture will start easier when cold but may be too rich to start when hot.

Have you done basic trouble shooting when it won’t start? Do you have spark when hot?

[Garrettvr507]

Check CHT for proper resistance when hot

Never mind - carbed (IMG:style_emoticons/default/chair.gif) - just learning to read (IMG:style_emoticons/default/biggrin.gif)

How do plugs look? Is it running super rich? Rich mixture will start easier when cold but may be too rich to start when hot.

Have you done basic trouble shooting when it won’t start? Do you have spark when hot?

I've checked the spark plugs and they all have spark. There's a little bit of carbon build up on each of them so I do think I'm running rich. Not sure how to resolve that though. Perhaps a carb tune?

[Superhawk996]

Here’s the thing - carbs by themselves rarely result in a no-start. They are a simple mechanical device.

When hot - have you verified you have fuel in the float bowls? Can do this by pumping carb and observing that accelerator pump jets have a steady stream of fuel when you pump the throttle linkage.

With carbs you can operate throttle to WOT and induce a leaner mixture as you crank. Similarly (with a helper) you can choke the carbs with palm of a hand to induce a richer mixture. One or the other of these should result in starting.

If you’re convinced you have spark (and proper timing) then the it is most likely to be fuel or compression issue.

If an engine has compression, fuel, and spark (in proper sequence) it has to run.

Start with basics

Verify valve clearances (cold)
Verify compression (cold and hot)
Verify static timing (7 degrees BTDC)
Verify you have fuel in the float bowls when hot and set at proper level
Synch and balance carbs

Post picture of plugs

What jetting / Venturi’s are you running?

[technicalninja]

I'd look down carbs hot and operate the throttle.

See fuel spraying out of accelerator pump nozzles?

I'd try a hot start with no throttle actuation and add a small squirt of B12 carb spray down all throats.

No spray, starts on B12: you have accelerator pump issues. Carbs are coming off.

Sprays, does not start on B12 hot I'd look towards ignition.

I'd pull plugs first and make sure they are not dripping wet hot.

Wet? Way too rich, maybe float level, definitely carb related.

Dry plugs, accelerator pump working, doesn't start hot on B12, and starts cold I'd be messing with primary circuit and coil.
At this point I'd be scratching my head as well.
Coil and condenser can fail only when hot but that is way weird.

[Superhawk996]

I'd pull plugs first and make sure they are not dripping wet hot.

Wet? Way too rich, maybe float level, definitely carb related.

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I sort of assumed you had pulled plugs when hot to check but there is a big difference between having spark at a wire vs at the plug.

[technicalninja]

@Superhawk996 , did you edit your post above mine?

Your "basics" are BAD ASSED!

You even want both hot and cold compression!

Adjust valves FIRST!

If everyone did what you suggest first, we'd lose 75% of the "why won't it start" threads.

His SUGGESTIONS are "THE PROPER WAY" for beginning diagnosis on any ICE in my book!

Only thing I'd add is:
If one or both of the compression tests has wonky numbers add a leak down test to the initial diag...

[Superhawk996]

@Superhawk996 , did you edit your post above mine?

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I almost always end up editing after initial post to either correct typos or to add / clarify information. Like I did with the strike through. If find it hard to do a single post and get it all written down in a sensible way on my first try.

If I’m wrong on info - I do leave up erroneous info and correct my mistakes with a PS note or edit marker

[rhodyguy]

Show a picture of your fuel pump and its location. Might as well show the linkage too.

1. Turn key to first position, hear pump run, the pump should cease running. Leave key in first position.

2. Slowly (not 3 quick stabs) fully pump gas peddle 3 times.

3. Engage starter. Feather throttle. A minute or so, the engine should idle on its own.

What is the idle RPM when warm?