Help me diagnose a problem

lippy · #1 (**permalink**) 09-25-2016, 01:26 PM

Hey Gents,

I took my car out two weeks ago to lunch (Alice's!) and when I got back in the car after lunch, it wouldn't start. It would turn over, I could hear the fuel pump, and there was gas in the float bowls. For some reason, I decided to shut the fuel pump with the manual switch I installed, and it fired right up. I then started the pump while the car was running and drove the car home. At the time, I thought maybe I just pumped the gas pedal a bit too much and flooded it. I never had this problem in the past.

This morning, I went to take the car out again. Starting the car cold was more difficult than it usually is, but it started. I then drove 2 mi to fill up. When I tried to start the car again at the gas station, same problem. This time, I hadn't pumped the gas pedal, at first. It would turn, but it wouldn't fire. I then shut the pump but it still wouldn't start. Again, there was gas in the bowls, and I heard the pump. I took the air cleaner off, and I could smell the gas, but I couldn't tell if it was flooded. Sort of seemed like it was, but hard to tell. Eventually it started, not sure how, and I drove it home.

I'm planning on taking the carb off to see if there is any debris. There also is the slight possibility it is the MSD box I installed about a thousand miles ago, but I think its a carb problem.

Any ideas?

Thanks!

bobcowan · #2 (**permalink**) 09-25-2016, 02:24 PM

Quote:

Originally Posted by lippy

Hey Gents,

I took my car out two weeks ago to lunch (Alice's!) and when I got back in the car after lunch, it wouldn't start. It would turn over, I could hear the fuel pump, and there was gas in the float bowls. For some reason, I decided to shut the fuel pump with the manual switch I installed, and it fired right up.

My first thought is that the electric pump is pushing enough fuel to keep the needle open and overfill the bowl. I would check the floats, and the fuel pressure.

Gaz64 · #3 (**permalink**) 09-25-2016, 03:16 PM

Sounds like fuel line debris trapped in the needle and seats.

What carburettor?

What fuel pump?

lippy · #4 (**permalink**) 09-25-2016, 03:27 PM

Quote:

Originally Posted by Gaz64

Sounds like fuel line debris tapped in the needle and seats.

What carburettor?

What fuel pump?

Weldon pump with bypass regulator at rear and dead head regulator at front (to knock down pressure). Carb is a Braswell (Holley type).

Gaz64 · #5 (**permalink**) 09-25-2016, 03:36 PM

Are you willing the inspect the carb needle and seats?

Have the float levels been check recently?

One the needle o-rings could also be damaged.

How much rubber line is between the last fuel filter and the carb?

lippy · #6 (**permalink**) 09-25-2016, 03:57 PM

Quote:

Originally Posted by Gaz64

Are you willing the inspect the carb needle and seats?

Have the float levels been check recently?

One the needle o-rings could also be damaged.

How much rubber line is between the last fuel filter and the carb?

Absolutely. I've had this carb apart several times, very comfortable with it.

The float levels are good. On a Braswell carb, you actually check them with a caliper to get them spot on, but of course I'll verify.

There is no rubber in the fuel system. It's all Aeroquip PTFE/braided line and hard line. A also cleaned out the lines thoroughly when I installed the system, 3-4k miles ago.

Gaz64 · #7 (**permalink**) 09-25-2016, 04:05 PM

Sounds like you have a good system there.

Should be just a little tickle up now.

I would run the engine, and then observe the boosters for fuel drip after engine shutdown.

The offending bowl will show up that way.

Gary

LG57 · #8 (**permalink**) 09-25-2016, 05:27 PM

I have had hard starting caused by corrosion inside the distributor cap. Might be worth a quick look.

PeteF · #9 (**permalink**) 09-25-2016, 05:32 PM

A faulty coil can cause intermittent starting issues.

lippy · #10 (**permalink**) 09-25-2016, 05:42 PM

Quote:

Originally Posted by Gaz64

I would run the engine, and then observe the boosters for fuel drip after engine shutdown.

The offending bowl will show up that way.

Gary

Thanks Gary. Not sure I understand fully. Could you please provide more detail?

On the other points, I agree the ignition could potentially be the issue. It's MSD, and inf c nothing changed to a different box.

Kit Coyle · #11 (**permalink**) 09-25-2016, 05:52 PM

Lippy...I had a similar problem but with a Holley double pumper fed with a
mechanical fuel pump. After checking coil resistance etc., I traced the problem
to junk between the float needles and seats which caused overfilling of the
float bowls and flooding. I pulled the needle/seat units and cleaned them. I
also found the floats set too high and reset them with the engine running
which is, I believe, better than setting the floats dry with measurement. The
filters were clean so I suspect alcohol must be eating away at something in
the carb. This happened a year ago and has not reoccured.

Gaz64 · #12 (**permalink**) 09-25-2016, 06:24 PM

With the air cleaner off, if a bowl has flooding problem (needle and seat etc), then the booster venturis dribble fuel onto the throttle plates.

Then the engine needs to recover from the flooded condition at next startup, generally warm start.

Gary

lippy · #13 (**permalink**) 10-03-2016, 11:33 AM

A quick update: I took apart the carb and cleaned and blew out the float valves (and jetted up a size while I was at it). I also installed my fuel pressure gauge (I don't leave it on). The carb seems to be filling properly, and the fuel pressure to the carb is about 6.25 - where it should be. I started it up, drove it until warm, and went back home, as I didn't want to leave myself stranded. I let it heat soak for 10m and it started up this time. I also checked to see if the booster venturis were leaking fuel, per Gary, and they weren't. *Hopefully* the problem is solved and it was just a matter of debris in the float valves.

RockBit · #14 (**permalink**) 10-03-2016, 03:45 PM

Do you have an in-line fuel filter?

Gaz64 · #15 (**permalink**) 10-03-2016, 06:11 PM

Have you checked and adjusted the float levels as necessary after pulling the bowls off?

CHANMADD · #16 (**permalink**) 10-04-2016, 08:15 AM

They are called ...needle and seat......

Gaz64 · #17 (**permalink**) 10-04-2016, 03:41 PM

Quote:

Originally Posted by CHANMADD

They are called ...needle and seat......

Have you read the whole thread?

lippy · #18 (**permalink**) 10-04-2016, 07:17 PM

Float bowls are adjusted, spot on.

I have two large billet in-line filters. One by the tank and one in the engine bay. They aren't the problem. When the car wouldn't start, the bowls were filled properly. The engine wasn't starved for fuel.

Gaz64 · #19 (**permalink**) 10-04-2016, 10:31 PM

Ah, so now it sounds like an intermittent no spark while cranking condition.

Have you checked for spark when the no start occurs?

What distributor?

What MSD module?

Gary

Frank Messina · #20 (**permalink**) 10-06-2016, 11:06 AM

You don't indicate what you have for a distributor so I'll just throw this out there. I had a similar no-start hot problem with my pickup many years ago. Started okay cold but no go when hot. Traced it to a faulty pickup coil in the distributor that created an open when hot. Once it cooled off it would fire up again. I doubt turning off the fuel pump has anything to do with it anymore than slamming the glove box or twisting the gas cap. FWIW
Frank