Wife and I had a couple of kid-free hours Sunday. We were going to go canoeing, but she wanted to put the powerboat in the water for the first time since last Autumn. I bust a hump to get her (the boat) ready. Inexplicably, a horde of police cars had blocked our path to the river due to investigation of an "unlawful shooting." We drove around the problem, and arrived, launched, boated, fished, and exited the river. On the way home, the tow vehicle, a thoroughly modern 1985 Chevy C30 Dooley seemed a bit down on power, even given that we were towing a little boat. About a mile from home, it abruptly lost power, at which time I lifted the gas. Engine resumed running. The remainder of the trip home was a series of stutters. Truck ran tolerably well at cruise, but didn't like pulling uphill, especially at speeds over say 40 mph. I have a steep climb into my 25 mph neighborhood, but she pulled that no problem.
So, Chevy 350, Quadrajet, 100k miles. Both fuel pump and HEI ignition module have been replaced in the last few years, but I suspect one or the other given the symptoms and the dubious quality of aftermarket parts these days. What say ye? Ignition? Weak fuel pump? Something else?
Truck starts and idles fine. Battery is strong.
Clogged fuel filter is my guess. When you lifted off the gas, it released pressure on whatever gunk was blocking fuel passage.
Grtechguy said:
Clogged fuel filter is my guess. When you lifted off the gas, it released pressure on whatever gunk was blocking fuel passage.
I will resist the urge to be offended, you implying that there is "gunk" in my fuel system and all. 
Hmmmm. The fuel tank as well as the pickup is just a year or two old. Old one was rusty. I'm not even sure there's a filter inline, but checking at the carb inlet seems like a good place to start!
I would also suspect a fuel problem. Ethanol loves to gunk up the floats in carbs. I always run non ethanol fuel in my carb'd engines.
It does sound like a fuel problem, so the quick answer is to replace the filter in the carb first.
HEI distributors also have a history of breaking the small wires that come out of the pickup coil because they flex every time the vacuum advance moves. That gives a pretty abrupt jerk, and will stop doing it if you pull the vacuum hose off the distributor.
I had exactly that experience with a Chev 1 ton in the 70s. Started, ran and cruised fine, but died going uphill. It was the fuel filter, which would flow enough for low load running, but not enough for WOT uphill. Simple fix.
Okay, the only filter in the system is a small paper element at the carb inlet. It is squeaky clean. Not a flake of rust in it. I recall I replaced this filter about the time I put in the new fuel tank and pickup a couple years back.
I drove the truck Sunday, started it briefly yesterday, and was surprised more gas didn't drip out of it when I took the carb inlet line off. Would the gas normally drain back through the pump?
I'm suspecting the fuel pump. Can't rule out ignition.
My 78 would drain back down the line with the mechanical pump. I'm fairly certain thats probably NOT normal as everything else was broken.
I would test fuel pressure and volume at the carb.
Take the line loose, attach your pressure gage however it needs to be for your particular situation, and crank. You should see pressure almost instantly. IIRC, ~7lbs for carbed. (It's been a lot of years since I've had to do this) The pressure should hold for a few minutes.
If this checks good, use a coffee can, glass jar, etc. and test for volume. It should pump a very healthy stream half filling a pint jar in a couple of seconds.
Of course, do this outside with a second person and a fire extinguisher handy!
Sounds like the Ignition control module (ICM) to me also. They're cheap and an easy install.
alstevens said:
Sounds like the Ignition control module (ICM) to me also. They're cheap and an easy install.
yeah, I'm definitely leaning that way. Fired it up and bombed it around a bit. Several WOT pulls, and it's 100% normal.
I've never had a mechanical fuel pump fail that didn't leak. This one isn't leaking. And it's only a few years old.
Virtually every older vehicle with electronic ignition I've owned has exhibited similar symptoms at some point. Getting ready to order a new module and pickup coil.
Usually a failing mechanical fuel pump will result in long cranking times. At least in my experience.
dculberson said:
Usually a failing mechanical fuel pump will result in long cranking times. At least in my experience.
Agree. Fires right up.
Here's one for you old-school GM distributor guys: How do you get the centrifugal advance weights off? I've removed the rotor. Module is accessible, but I can't get to the pickup coil. How remove weights? TIA!
1988RedT2 said:
Here's one for you old-school GM distributor guys: How do you get the centrifugal advance weights off? I've removed the rotor. Module is accessible, but I can't get to the pickup coil. How remove weights? TIA!
Have to remove the distributor to remove the cam gear to pull the shaft out to change out the pickup coil. Springs need to be removed off the pin and then the weights should just pull off the plate.
Ranger50 said:
1988RedT2 said:
Here's one for you old-school GM distributor guys: How do you get the centrifugal advance weights off? I've removed the rotor. Module is accessible, but I can't get to the pickup coil. How remove weights? TIA!
Have to remove the distributor to remove the cam gear to pull the shaft out to change out the pickup coil. Springs need to be removed off the pin and then the weights should just pull off the plate.
Well, poo! If I have to pull the thing, I could just replace the whole unit!
https://www.jegs.com/p/JEGS/JEGS-HEI-Street-Spark-Distributors/755778/10002/-1?N=0&Ntk=productgroup&productId=755778&Tab=SKU&enginetype=4294799206&make=4294829791&model=4294827434&productId=755778&submodel=4294829637&year=4294829802&productId=755778
Steel or iron gear relevant?
Steel gear for roller cams.
Ranger50 said:
Steel gear for roller cams.
So iron gear for stock cams?
