LittleMack89

Hello, sorry for the long first post but this is driving me crazy. I have an 89 W150 with a 77 engine. It has electronic ignition with external Holley fuel pump feeding an edelbrock 650 carb. The engine is freshly rebuilt by me with a few smaller performance upgrades, proper machining and grinding, and a mild cam which I feel would have biggest impact on this issue. For maybe the first 5-10 cranks after install it would run great without fail, enough for me to break in cam and get first break in cycle. then it slowly started to last shorter and shorter during idle, and now it will only idle for about 10 seconds before abruptly shutting off, and there is no sign of its impending doom, sounds very health then just shuts off. I can fire it back up after a few seconds only for it to die again.

The ignition module and coil are running off a separate switch than the primary ignition due to my lack of electrical experience (I’m 16) but it works great and has its own relay and 20 amp fuse. Same with fuel pump but with 7.5 amp fuse as recommended by Holley for the 32gph mighty mite. Coil is msd blaster 2 designed to bypass ballast resister and run on 12v all time and icu is new but stock 4 pin blue box. Distributor is new as well, replaced it after issue started. I’ve checked everything ignition related while it’s running, as it dies, and while just turning motor over and spark isn’t the issue here (I am open to be corrected), everything read within .5 volts of battery which reads 12.67 volts as long as the switches were on. Battery is new and I put it on trickle charge about every other night so it’s usually good to go with I try some more cranking.

so I moved to thinking it’s fuel. pump is pushing about 6 psi at all times, fuel is fresh clean 89 octane, new fuel filter, the 6ft 3/8 fuel hose was replaced from tank to carb, and the carb is brand new but I cleaned everything out for good measures. I played around with idle mixture and did find it running much better, but still same issue

I next took valve covers off and observed valves opening as they should, and the springs were upgraded by machine shop when I sent in heads during rebuild and are fit for my cam. I’ve played with timing, and like the idle mixture I was able to perfect it while it’s running but it has not solved my problem.
I need help, I can’t for the life of me figure out what is going on.😢
Here is a video of what I am seeing and hearing;


(Edit) the knocking noise from engine compartment in video is fuel pump, can be seen in far side fender. Oil pressure is perfect

RacerHog

Fuel should be back by the fuel tank.... Electric pumps push better than they pull.....
However... Put a fuel pressure gauge in line up near the carb and check the fuel pressure.... I think you will find its low...
Or
You could also run a short hose from the pump into a 5 gal gas can and check the pressure just for testing purpose....

Coronet 500

Welcome.
I agree, do both don't assume your getting volume of fuel if pressure is good. I recommend buying an inexpensive vacuum gauge which is a good diagnostic tool to have.

If you feel safe doing it, spray some gas into primaries just as it is dying and if it picks back up lack of fuel is your problem. Good luck and report back.