Another cranks but occasionally starts thread...easy read

[ninjaturtle]

1976 2002 base

History: Unknown
 

Part	Mod	Condition
Motor/Carbs	Weber 38 DGES Electronic Choke Schrick camshaft (not sure which one)	Cleaned filter, carb all orifices, etc.
Fuel/Regular	Electronic Fuel Pump/Regular (Ireland Engineer possibly) Fuel Regulator -Mr.Gasket Fuel Presure Regulator	Age: Unknown but works and looks new
Distributor	Pertronix Electronic Ignition Kit	New
Valves		Adjusted
Coil	Bosch	Replaced
Compression test		Healthy all across
Timing		Set by shop
Spark Plug/ Wires	NGK Iridium? Taylor Spiro Pro 8mm
Battery	Tested and fairly new

Issue:

VIDEO HERE without throttle input. With throttle input it basically does the same thing, rpms might go up and down, it might turn over might not. Usually not but if I let it sit for awhile I might get lucky when I come back to try.

Vehicle cranks but fails to turn over. The issue is sporadic and there are no patterns which could point to this. The carb had been cleaned/tuned assuming that it was the carb. Spark plugs have been replaced and gapped to work for the MSD ignition. The fuel pump primes each time. The distributor was rebuilt and the coil was replaced but it continues to randomly decide not to turn over. Often times I have keep blipping the throttle assuming that not enough fuel is being fed and it still doesn't turn over. Sometimes if I continue to crank the motor while blipping the throttle for many many seconds 5/10+ it eventually tries to turn over but want's to stall out. I force the rpms up so it doesn't stall and after a few seconds it runs. Othertimes this doesn't work.

Example: I drove to the store just now and it worked just fine. I spent 10 mins in the store, came back and the car was having this issue again. At this point I'm not sure what it could be. The battery, starter and all check out just fine and there is spark across all plugs.

Have spent thousands at the shop and now I am really looking for a knowledge sessions from the community. Greatly appreciate everyone who has taken the time to read this and chime in.
 

 

 

Edited February 13, 2021 by ninjaturtle

[2002iii]

First a few questions:

What brand and model coil? Fuel pump? Regulator?

 

Have you looked at the coil wiring? Inline resistor wire?

 

Are you using points in the distributor?

 

How is the fuel pump wired? Inertia safety switch?

 

Is the choke on the 38/38 functioning correctly?

 

Are you running the factory air cleaner?

 

I would also check the wiring for the coil voltage boost from the starter and ignition switch wiring. If your ignition switch sparks and/or smells burnt it has an internal short and needs to be replaced.

[dlacey]

ignition timing or firing order wrong

[Rodolfo Lasparri]

Have you blown out the fuel line from the tank forward, checked the fuel filter to confirm it’s not plugged up and looked at the tank pickup screen? If you have done all of those then I’d look at the ignition coil and confirm pertronix is working properly.

[roadhog0]

Float level set right? My car would do this hot when the float level was too high. The gas would boil in the bowl then percolate out into the intake and flood it. I'd come out from the store and have a hell of a time restarting it.

[Mike Self]

An intermittent no-start situation is either spark or fuel.  Your timing suddenly didn't change, nor did you suddenly lose compression in all four cylinders, so concentrate on spark and fuel.

Next time it happens, immediately do this:

1.  check for spark at (any) plug.  If no spark, you've got an intermittent problem somewhere between the battery and the spark plugs.  Work backwards from plugs to dizzy cap to pertronix to coil and then to the low voltage component to make sure the coil is getting power.  If you have spark...

 

2.  Remove the top from the air cleaner and work the accelerator linkage while looking down the carb throat--you should see a squirt of fuel from the accelerator pump nozzle every time you work the linkage...no squirt = no fuel in the float bowl.  Work backwards from the carb through the fuel filter, fuel lines, fuel pump all the way back to the gas tank.  It could be something as simple as a loose hose clamp on a fuel line.  If you have a squirt... 

 

3.  Pull the idle jets, make sure they're clean and squirt some carb cleaner into the passages.  Trash in those itty-bitty orifices can cause intermittent starting problems...

 

4.  Did you make sure the carb is fastened tightly to the manifold, and there's no air leak between carb and manifold?

 

That's all I've got...

 

mike

[Mark92131]

Are you running a new coil with an internal resistor, (Blue Coil)?  If so, you will need to remove and replace the resistor wire as @2002iii pointed out.  I have also had problems with the Pertronix.  You need to make sure that the ring on the distributor shaft is seated properly so it is the same height as the Pertronix pickup and gapped correctly (030?).  What distributor are you running?  Nice that the shop set your timing, but buy a timing light and verify that it is set correctly for your distributor.  Who adjusted that Weber 38/38, so hard to setup properly, especially with a stock 1976 engine with standard internals, easy to flood with a weak spark.  Also, what plugs are you running?

 

Mark92131

Edited February 9, 2021 by Mark92131

[TobyB]

When it does it, does flooring it and cranking speed the process?

 

t

cranks and turns over are what it does before it catches. 

 

or catches fire.

[02jake]

Mike has some good advice. I had a similar issue with my 72tii. It would start normally when cold. after some city diving I would shut the car off, come back it would not start. Wait a couple of hours and it would start as normal.. Check all the basics, fuel flow, fuel pres. spark, nothing seamed amiss. Pulled plugs soaking wet. Lost trust in the car.

 

My son takes it out one day and this time could not get it started. Put the car in the shop, changed plugs, pertronix and coil, fuel filter. Still same problem flooding. Pull plugs and they are soaked. Got Tyler to help, did a compression test #1,2 normal, as we got to #3 dead battery. That's odd had no indication the battery was bad. Pulled it out put it on a charger o/night. Next day tried the compression test same thing. Installed a new battery started right up, set the timing and it hasn't skipped a beat.

 

Did some google research and there is some info on the early pertronix  being battery voltage sensitive.

 

Hope this helps. 

Jake

[TobyB]

Jake, it's just low- vapor pressure fuel in the pressurized fuel line

boiling, flooding the float bowl, and then the engine.

 

The immediate fix is to floor the fucker, and crank until it catches.

Usually takes 15- 20 seconds.  You end up keeping it floored for

longer than seems prudent to get at least 3 cylinders dried out.

Pathetically, this also works on the M54 in the E46s...

but you're cranking for 45 seconds to 2 minutes.

 

Longer term, lowering the float level a little (and tuning for that)

fitting a very good quality float valve,

then running a bypass fuel system and an electric pump seems

to usually cure it.  It's a lot of hassle-

but we live in unenlightened times.

 

t

low expectations.