Engine trouble

jumper · Post by **jumper** » Fri Jul 13, 2007 6:02 pm

so i changed to a four barrel setup with a holley 600 cfm carb the carb was setup by a local shop. i drove 5 mins to the highway 10 mins on the highway, off the highway the engine dies at the second set of lights 30 sceonds apart.
It will start after 5-10 mins but if you touch the pedal it might die then or will wait until you are at a set of lights with traffic behind you if you start it from cold and just give it enough gas to start up then don't touch it it will die after about 12-15 mins. The carb shop reckons it could be the coil heating up and giving spark problems and not the carb so i swap in the old coil same problem.

any ideas?

how hot should a coil and ballast resister get?

chev 350
holley 1850 600cfm
old coil: standard coil and ballast resister
newer coil: pertronix and ballast resister to go with the ignitor module

Goose · Post by **Goose** » Fri Jul 13, 2007 6:24 pm

hmmmm, did the carb shop actually look at it after the first problem? Have you checked that there's gas in the bowls and it feeds into the throat? (when you give it a bootful, not running) electric fuel pump or manual?
If it's electric, might not be feeding enough fuel to the bowls, therefore running till trhe level drops enoughto stop it from runing..... manual pump could be buggered/slightly buggered, and doing the same as above......

Mattman · Post by **Mattman** » Fri Jul 13, 2007 6:25 pm

Still sounds like a fuel problem to me. Almost as if you are boiling the fuel and it is vaporising.

Do you have a site glass on the carb?

Where is the fuel line run?

Matt.

Goose · Post by **Goose** » Fri Jul 13, 2007 6:40 pm

yeah, what he said (above) also, ballast and coil will get quite hot, but if they're melting..... :shock:

xorph · Post by **xorph** » Fri Jul 13, 2007 6:55 pm

sounds like vapour-lock
used to happen to bigblock in dad's boat every time he turned it off and tried to start it.

Can happen if you have routed your fuel line near or on something hot.
this means the fuel pump ends up sucking vapour instead of liquid and yeah engine no work...
Happens at idle and when you shut off engine, cos fuel stays where it is in the line so a single section of fuel has time to heat up and vapourise

jumper · Post by **jumper** » Fri Jul 13, 2007 6:56 pm

Fuel line is run from mech fuel pump, cable tied to the batt tray then with out touching anything to the carb.

The carb guy said he had set the floats.

Sight hole is on the side of fuel bowl fuel should be level to the bottom of hole.

Sadam_Husain · Post by **Sadam_Husain** » Fri Jul 13, 2007 6:59 pm

best coil you could get for it would be to swap the whole dizzy over to an HEI distributor, the coil sits in the top of the cap and it dosent use any mechanical points, you set the timing once and never worry about it again and the HT side puts out about 500,000,000 volts to the plugs :fire:

Goose · Post by **Goose** » Fri Jul 13, 2007 7:04 pm

Sadam_Husain wrote:best coil you could get for it would be to swap the whole dizzy over to an HEI distributor, the coil sits in the top of the cap and it dosent use any mechanical points, you set the timing once and never worry about it again and the HT side puts out about 500,000,000 volts to the plugs :fire:

Yeah yeah!!! What HE said!!! HEI is the dogs bollocks :twisted:

I had a twin point mallory, dumped it for an electronic ignition.

Set and forget.
'Nuff said!

xorph · Post by **xorph** » Fri Jul 13, 2007 7:09 pm

hmm..
I can remeber when i fitted a holley 2 barrel to my p76 i had initial greif trying to get pressure right.

think your supposed to have 4 psi (? anyone?)
and if way too high it leaks past float valve and can flood engine.

opposite which is prob more likely is your return line is not restrictive enough and your fuel pump is draining back to tank when it idles instead of filling float chamber.

Try pegging off your return line maybe?

Mattman · Post by **Mattman** » Fri Jul 13, 2007 7:47 pm

Before spending money eliminate the easy things.

Probably doesn't have a return line so nothing to check there.

When it won't start or dies jump out and check the site glass, you should see fuel in it, if there is no fuel then that's why it won't start.

Most mechanical pumps run about 3-4 psi, if there is no fuel in the float chamber then your pump might be tired and or you are getting fuel vapourisation. A tired pump will usually show itself under load or cold starting but should idle fine and hot start fine.

Matt.

Steve_t647 · Post by **Steve_t647** » Fri Jul 13, 2007 7:52 pm

still sounds like fuel, spark you would feel missing and backfire in headers and muffler (pumping unburnt fuel into exhaust), how rich does it smell did they get the idle fuel mix right?

Also look at the fuel filter in case the flow shook some crap loose.

Good Luck

jumper · Post by **jumper** » Sun Jul 22, 2007 5:41 pm

Went to the 40 the other day and it would not start at all, the starter would crank the engine over but would not fire i think i have it down to the coil. Tested the coil with wire from coil + to batt +, ht lead to ground and wire to coil - touched to ground, there was a tiny spark. so need to replace coil :roll:

Mattman · Post by **Mattman** » Sun Jul 22, 2007 7:44 pm

Come and see me next saturday Jumper and I will sort you out.

You running an external ballast or not?

Matt.

jumper · Post by **jumper** » Sat Aug 11, 2007 11:13 pm

After lots of fiddling and putting the points back in the engine runs

i left it running for about 30 mins and it did not cut out like before but still has a back fire through the carb if you stomp on the skinny pedal.

The other day a mech had a look at it before it was running and said that the accl pump in the carb had a problem, when you look down the throat of the carb and move the accelerator the left spray of fuel is a fine spray but the right side is a bit of spray and drops of fuel. Could this cause the hesitation and backfire out the carb?

Mattman · Post by **Mattman** » Sun Aug 12, 2007 7:18 am

Nice one jumper, time for some skids!

The accel pump is usually the cause of hesitation. Now that it's running you should be able to take it back to the carb people for them to have another look at it.

Matt.