350 Chevy Problems

taxpyer · December 16, 2011, 03:09:35 PM

Feel the flex line from the frame to the fuel pump at an idle, if it pulsates the hose is shot and is sucking flat under load.. Had this problem on a sbc few years ago.
Good luck.

oj · December 16, 2011, 04:44:56 PM

Gas cap vented? See if some mud daubers have nested in there and you are trying to pull fuel from a vacuum - likely not but it does happen.
Can you tee your fuel line from pump to carb and run a temporary gage to where you can see it while driving? and confirm fuel is available to carb at all times? What kind of carb?
Unilites can be voltage sensitive, they generally take the guesswork out by burning up but maybe the voltage to the unit is intermittant or drops below a threshold. An electrical gage temp'd where you can monitor it might be helpful.
Thats about it, you need air, spark and fuel and like meatloaf said, 2 out of three ain't bad!

48bill · July 17, 2012, 04:34:51 AM

Thought it was fixed. Bad ballast resister.

Have put about 700 miles with no probs since the fix. A month ago it seemed to be starving for gas one night. Thought bad gas but not the case. Replaced fuel filter even though the filter looked good and after cutting up still looked good.

Last night, hot 95 + high humidity drove about 10 miles and started again. Eventually stalls out but restarts. Pulled filter out. After sitting for 30-40 minutes seemed all OK. Drove 5 miles to a cruise night,no prob. After being there for an hour drove another 7 miles started to not get fuel again. Waited 30 minutes and started home after 8 or so miles started again. I'll check rubber hoses again, replaced with VITRON ones 4-5 years ago.

Thoughts???

wayne petty · July 17, 2012, 07:58:31 AM

a few things...

back to the FULL flow testing...

do you have a fuel pump pressure tester similar to this??

http://www.harborfreight.com/fuel-pump-and-vacuum-tester-93547.html

this is a compound gauge.. it will measure 30 inches of vacuum or 15 pounds of pressure.

or do you have a hand vacuum pump..

http://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-69328.html

where you can hook a vacuum gauge to the fuel pump inlet.. crank.. the engine... see if the fuel pump builds over 15 inches of vacuum... then holds it for a while..

if you have the compound gauge.. do the see if it will hold pressure ..

i am thinking that you might have some really fine sediment that is getting through the conventional fuel filter before the pump.. so the fuel pump check valves are not properly sealing and the pump is loosing its ability to properly suction the fuel up and then pressurize it out..

do you have any magnets stuck to the bottom of the fuel tank.. either inside or outside??? i dropped a small supermagnet into some fuel i poured out a fuel filter..

notice the Red dUST.. attaching its self to the magnet.

a big honking speaker magnet stuck to the bottom of the fuel tank works great on the outside. keeps all the Red dUST trapped inside the tank in one spot..

installing a fuel injection type of inline fuel filter before the pump.. as the fuel injection spec fuel filters have a much tighter filter media.. then doing the full flow fuel pump test will flush out the any sediment from the fuel pump check valves..

its important that you get almost a PINT of fuel during the full flow test.. this proves the fuel system can supply enough fuel for the engine..

if you have a restriction.. before the fuel pump.. the pumping action will create lower that atmospheric pressure in the line between the pump and the restriction and cause the the fuel to boil and vapor lock will happen.. this suction side vapor lock will push all the fuel in the lines all the way back to the tank and leave the pump HOT and almost dry..

vapor lock can happen on either side of the fuel pump..

if the fuel pump does not build as much pressure.. the heat on the carb side of the line will cause the fuel to boil in the line and expand faster than the fuel pump can push more fuel in... faster than the needle and seat can let it through..

Mikej · July 17, 2012, 01:27:13 PM

Could be vapor lock? Can you pull the air filter and see if your getting gas after it dies?

chimp koose · July 17, 2012, 07:09:01 PM

How about a plugged/restricted fuel tank vent? did its line get replaced when all the others were?

48bill · July 24, 2012, 08:48:12 AM

Replaced the fuel pump and problem seems to have gone away. Keeping my fingers crossed. I also checked the hoses and vent.

Thanks for all the help

Replacing was simpler and cheaper than buying the test equipment. I know shame on me for not testing. 40 years ago when I was in the Army I criticized my motor pool mechanics for replacing parts and not throughly diagnosing the problems and now I do the same myself. Sometimes it was OK in the Army due to operational needs not so now when no one is shooting at me.

48bill · August 29, 2012, 11:43:38 AM

Fuel pump was not the answer.
Got stuck and needed Triple A flat bed. Towed to my local garage. When there started right up and ran fine. Had cooled off for an hour.
Then seemed the problem narrowed down to electrical and when hot (200+ degrees).
Testing found that the wire from the ignition switch to the ballast resister was at 13+ volts cold and 7-8 volts when heated up (30 minutes at idle in 80+ degree temperature). Not enough juice coming out of the resister for the UniLite.
Replaced the wire and moved coil off of intake maniofold to firewall. Seems to have fixed it. Stay tuned to my ongoing saga.

wayne petty · August 29, 2012, 01:23:14 PM

is there a chance that the coil primary was shorting out do to Heat building up .

you might want to monitor the voltage on the primary with a temp install of a volt meter gauge... just to that..
some gauge like this..
http://www.harborfreight.com/in-dash-voltmeter-95779.html

just on a bracket with a magnet on the base..

or that the bulk head connector is damaged .. or the ignition switch is damaged.. limiting voltage after it gets hot. .

48bill · September 18, 2012, 12:31:35 PM

The last fix has seemed to eliminate the problem. Put on 150+ miles without a problem. Ran it to over 200 degrees and still close to 14 volts to the ballast resister.

Thanks for all the suggestions. This is a great place for the baffled like me types.

48bill · November 30, 2012, 12:29:16 PM

A QUESTION after a statement of new info: :?
Since my last post I went 450+ miles without a problem then on a reliability run in early October the bad hot rod gods got me. Car stopped running and smoke poured out from under the dash. I shut it off, turned the battery switch off and grabbed the extinguisher. Fortunately no fire. After a tow home I eventually found that the wire from the ignition stitch to the ammeter burned up. All the insulation on it was cooked.

I hot wired the car to move around the past couple of months without a problem. Yesterday I was going to a friends to fix(heated garage) the wiring. I found that the battery had apparently died. Charger showed in the danger zone. Melted the soft metal (lead) connector of the ground cable at the battery post.

After some investigation it turned out that the positive wire from the trunk mounted battery to the firewall mounted Ford solenoid (hot start cure) was rubbing on the frame and shock mount and had frayed and was shorting out. Problem solved for the day.

MY QUESTION. Could this have been the cause of all the problems I had been having over the past year and a half?

wayne petty · December 01, 2012, 12:23:40 AM

hard to say... electrical shorts are usually very quick to show themselves..

i Personally HATE AMP meter installations...

Volt meters are far better.. and take almost NO current to operate...

do you have any fusible links protecting the wiring harness now... 6 inch pieces... 4 sizes smaller than the wire they protect.?

so a 10 gauge circuit is protected by a 6 inch long section of 14 gauge fusible link...

try to use the lower 4 parts of this test to verify the ground side.. and then do it on the positive side also..

alternator output to the battery positive... with everything on.
ignition switch to the battery positive ... with everything on..
post results.. measure at 20 volts dc.. then 2 volts dc..

since you have a rear mounted battery... use a single side of a jumper cable laid beside the car.. to hook your digital volt meter to .. the jumper cable will usually not throw the readings off as there is NO current flow other than the 1/100,000 of an amp the volt meter needs... please be careful not to touch the chassis or body with it..

or create a long long test lead with components from electronics stores..

wayne petty · December 01, 2012, 01:05:22 AM

lastly... what kind of ignition switch are you running currently??

is it burned out?? or up???

i am taking its dash mounted..

is it something like this

this is whats called for a 54 chevy???

i cobbled this together for other forums to replace points style ignition switches that open the IGN 1 contact when the ignition is turned to the cranking position.. this is for HEI ignition systems... so it needs 2, 12 gauge wires to supply it.. and a 12 gauge wire out of the ign 1 to the ignition system. doubling up the battery supply reduces the load on the individual connectors ..

the bezels are available ..

if you are VERY Creative... you might be able to create a threaded bracket to mount this later switch to the dash like the first pictures are above... you might be able to do it with set screws ... Pointed ones. in drilled depressions.. to hold it to your custom bracket..

48bill · December 02, 2012, 11:50:22 AM

Wayne,
Thank You again.

I am running a generic after market accessory ignition switch.

I will try the suggested test after i do some rewiring and eliminate the ammeter and instal a voltmeter. Right now I move the car around by hot wiring so no lights or charging system. Will not be able to fix til Monday and will run suggested tests then.

wayne petty · December 02, 2012, 05:58:51 PM

no charging system... i worry... that the alternator is completely UNPLUGGED from the electrical system

or at least the OUTPUT terminal is properly connected to the hot side of the battery..

when the output wire becomes disconnected.. any amount of charging current the alternator is putting out will at that instant stop being amperage and become VOLTAGE... as the load is gone..

this creates a high enough voltage to short the or open the diodes .. in most alternators....

i will explain this for the entire forum..

most alternators are created with rectifier diodes... 3 positive and 3 negative .. these are usually rated at 25 amps at 100 volts PIV... Peak inverse volts.

some rebuilders use increased rating on the diodes...
6 x 50 amps x 200 Volts piv..

the voltage above the rating of the diodes can be created in a split second as the voltage regulator controls the size of the magnetic field spinning in the rotor... it pulses this current to the brushes and the rotor winding.. there is a slight delay in changes in current and voltage needs..

so if somebody pulls a battery cable off with the engine running.. if the alternator has some output at that moment in time.. before the voltage regulator can reduce the current to the rotor... the voltage goes upwards and can easily peak well over 100 volts.. blowing out the diodes.. or Shorting them .

the diodes... the stator windings create AC voltage as the rotor spins and the magnetic fields move thru.. this creates AC voltage on the 3 or 4 sets of overlapping windings.. one end is usually bound together and is the stator terminal. the other ends are connected to pairs of diodes.. one positive and one negative.. any current above 0 ac goes through thru the positive diode and to the output terminal... any voltage below 0 goes through the negative diode and to the alternator housing.