Engine cutting out going up hills

My 2002 has not been cooperative lately. Out running an errand a few days ago, and every time I had to climb a large hill, the engine would start sputtering and then die completely. Flat or downhill and everything ran absolutely fine. Seems like a fuel problem.

I blew out the line back to the tank (clear), confirmed that the tank, pickup, and filter were clean, and made sure the tank vent line was clear. I plugged the fuel line at the pickup end and pulled 30 inches of vacuum on it from the engine end; no leaks. The car has dual Webers, which are fed by a Carter #4070 electric pump (6psi, so no regulator, 72gph rated). That flow rate says to me that I should see over a gallon per minute out of the pump. I ran the pump for one minute with the car level and got 2 quarts of fuel at the carb end. I then lifted the front end with a jack as high as it could go (maybe 18-20") and repeated the test; this produced 1.5 quarts over a minute.

I'm thinking this is a clear indication that the fuel pump is the problem here. Am I on solid ground with this diagnosis, or have I missed something? Just want to get eyes on the problem before I order parts. Thanks.

check the floats just in case they are sticking.

oldtin wrote: check the floats just in case they are sticking.

That's the first thing I thought too. But the jack stand flow rate diagnosis seems to be pretty damning of the pump and/or pick up.

I'd also check the voltage at the pump - the pump might simply not be getting enough juice to run at its full capacity.

IDK if that car has a cat converter, but if so....I recently experienced a similar problem (engine sputtering/stalling under acceleration especially up hills), and it turned out my cat substrate had broken loose and would slide back and block the exhaust pipe. Only happened going up hills or accelerating hard. Then would be fine when braking or going down hills, lol

Yours probably doesn't have a cat though, but figured I'd throw it out there.

Misfire under load? Most fuel problems are electrical right? (or vice versa). Check coil / dizzy.

KJ

Thanks for the suggestions.

The coil was new last year, so I'm thinking that's OK. I'll have a look at the rest of the ignition system, but nothing in there has many miles on it, and I've got a Pertronix electronic trigger instead of points.

No catalytic converter on this, so that's not an issue.

I'll pull the covers off the carbs and check the floats, as well as checking the voltage at the pump, tomorrow. I'll let you know what shows up. Thanks again.

02Pilot wrote: I'll pull the covers off the carbs and check the floats, as well as checking the voltage at the pump, tomorrow. I'll let you know what shows up. Thanks again.

Don;' just look at the float, move them around and make sure the don;t have any weight to them. The newer style float replacements that some cars have can be crap and they really soak up the fuel without showing significant cracks.

Kendall_Jones wrote: Misfire under load? Most fuel problems are electrical right? (or vice versa). Check coil / dizzy. KJ

For newer cars at least, ^this. We had a heck of a time finding a random misfire, it was a v8 grand Cherokee, that would only misfire under lightish load up a hill, and it had had the coil packs replaced recently. The slushbox would kick down and cover up any sort of even slight load low rom missfire, but it was the coilpacks. Just cause its new doesn't mean its good.

I am thirding the floats.. they can be tempermental to inclination changes if marginal

1.5 quarts per minute is about 157lb/hour, which is enough fuel for roughly 300hp...

but you checked it at zero PSI. Check it again with pressure on it. (Simple to do - pull the hose off again, stick a regulator on the end, measure what comes out of that)

The fact that elevating the nose put enough of a load on the pump to significantly reduce flow indicates to me that if you were to regulate it down to 3-4psi, you'd get nothing but a trickle. Enough to run the car on, but put a long constant load on it, and you'll drain the float bowl...

Can you hear the fuel pump run? If so is it running steadily when the car quits running? If so, it would appear to be fuel starvation.

Years ago I tuned up a Chevelle 350 and at the time I thought spark plugs were spark plugs, WRONG! I bought them at K-Mart. So I got another set from a parts store and the cutting out under load stopped occurring. Later, I met a Champion SP rep. who told me that the best plugs went to the OEM mfgs. then down to discount stores who got the worst performing plugs. According to him all Champ. plugs were tested under load and that was a major determining factor relative to quality.

OK, here's what I've found:

The pump is getting full voltage and the ground is good. The pump runs steadily throughout.

The floats are the old-style brass ones, and they are not leaking or damaged. They move freely.

I don't have a pressure regulator to test the flow from the pump.

I'll have to dig up the spec on the coil; it's a Bosch KW Red unit. Having just had the experience of having old coil fail on me last year (cutting out under load), I can say that this feels different. The coil failure would cause misfiring, but as soon as you let off it would be fine. This problem just gets progressively worse until the engine dies completely; as soon as I get it on level ground, however, it starts right up.

Any last thoughts on this before I pull the trigger on parts?

Just a thought brought up on another forum. How much fuel in the tank ?

Should the pump really run all the time? I might be misreading your post though...

My understanding is that with a carb'd car the pump runs until the float shuts off the fuel supply, then restarts when the float opens the fuel supply again.

Plenty of fuel in the tank.

It's a rotary vane pump (this one: http://www.summitracing.com/parts/CRT-P4070/ ). It runs all the time, as would a mechanical pump. The needle valves controls whether fuel flows into the bowls.

BoxheadTim wrote: Should the pump really run all the time? I might be misreading your post though... My understanding is that with a carb'd car the pump runs until the float shuts off the fuel supply, then restarts when the float opens the fuel supply again.

every carbed car I have had... the pumps runs continously, whatever is not used gets recirculated back