Accelerator pump

chevrolet

#1

I think my accelerator pump is shot. Does anyone know how hard it is to replace or how costly it is to get something like this replaced (time estimate especially)? I’m fairly good at replacing parts once a problem has been diagnosed–and someone I trust diagnosed this one–but my tools and time are limited. Thanks for any input.


#2

Make, model, year would help a lot. The only accelerator pump I’ve replaced was in a carburetor. What are the symptoms?


#3

It’s a 1986 Chevy K20 pickup. It died one day while driving, just lost power. It started and I got it home. Then it would idle but if I put it in gear it would die. Then it wouldn’t even start. I checked the EGR valve, fuel pump, fuel filter. I looked for cracks or holes in hoses, found none. I’m not seeing fuel in the carburetor, so my girlfriend’s dad said it was likely the accelerator pump. I’ve never worked on a carburetor, though, and I’m not even sure where this thing is.


#4

Pour a little bit of gas into the carburetor and see if the truck starts. If it does and immediately dies, then you may not be getting fuel to the carburetor. If it stays running, pull on the accelerator rod and see if you see fuel squirting into the carburetor. If you do, the accelerator pump is o.k.

If the truck immediately dies, disconnect the fuel line from the carbuetor and direct the output into a can. While someone operates the starter, see if fuel squirts out of the fuel line. If it doesn’t, your problem isn’t the carburetor.

The accelerator pump in the carburetor comes in a rebuilt kit. I haven’t bought a carburetor kit in 35 years, but my guess is that the price is around $50. However, I don’t think that is the problem.


#5

Thanks for the reply, but I checked the fuel line going into the fuel filter. It’s fine. I really just need the amount of time it might take to replace the part and, I guess, info about whether I would need any special tools. I’ve never taken apart a carburetor before.


#6

Registering on www.autozone.com gives you access to an online repair manual for the K20. Here is a link to the carburetor page.

http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?chapterTitle=Carbureted+Fuel+System&partName=Fuel+System&pageId=0900c1528004c50f&partId=0900c1528004c4a3

It looks like a Rochestor 4 barrel. In years past, I haven’t had much luck with rebuilding or buying rebuilt carbs. I usually ended buying a new one, it’s a lot less aggravating. I had the same symptoms with an 82 Nissan pickup and the carb had a bad accel pump. I could have bought a new carb with what I paid the shop to fix it.

www.summitracing.com has rebuilt Holleys for the 5.7 V8, but they’re not cheap.

http://www.summitracing.com/search/year/1986/make/CHEVROLET/model/K20-PICKUP/Department/Air-Fuel-Delivery/Section/Carburetors/Engine-Type/V8/Transmission/Automatic/?Ns=Rank|Asc

Good luck,

Ed B.


#7

Did you check the fuel line pressure?

prop the choke open, look down into the primaries with a flashlight, and manually operate the throttle linkage as if you were pumping the pedal. If you see a spray of fuel, that means that you have fuel in the float bowl and your accelerator pump is working. If you do not have spray, that means that either the pump is not functioning or the bowl is empty…no fuel supply. You need to first determine this. It’s possible that your fuel pump is simply plugged. I’m hoping.

This accelerator pump is, I believe, internal to the carburator housing and will require substantial tear-apart to replace it and thus basically a rebuilding of the carburator.

The other factor to consider is it may not be the accelerator pump. If your float is stuck in the up position or the inlet valve (needle valve operated by the float)is malfunctioning (stuck closed) you’ll be unable to fill the bowl.

A word of warning: if you need this vehicle, I’d advise you to buy a rebuilt rather than try to rebuild this one. IMHO rebuilding a 4bbl carburator and getting it running right again is among the most challenging projects for a beginner. You should be able to get a rebuilt for about $200-$250 (after core credit). It’s worth the cash.

If this is an extra car then by all means get a good Rochester rebuild manual and have at it. But understand that this is a project, not just a bolt-off/bolt-on parts replacement.

Just my humble opinion, you understand.


#8

You won’t know the fuel pressure until you measure it with a gauge. The fuel pressure value is in the repair manual. Got one?
Even if there is the correct fuel pressure up to the carb, fuel may not be making it through the little filter in the carb fuel inlet port (on some carbs). Replace that filter (if there). There should be a fuel filter somewhere in the fuel line. Replace that, also.


#9

If this indeed a fuel problem, the stuck float idea makes sense. Sometimes, tapping on the carburetor float bowl with a stick will release the float. The way the truck died out doesn’t sound like an accelerator pump to me. To me, “carburetor” is a French word that means leave it alone.


#10

You said in an earlier post that you checked the hoses. Did you check down at the gas tank? I had a hose deteriorate down at the gas tank. I went through the same symptoms that you describe. The engine was sucking air. For a while I could start the car by priming the carburetor. It still sounds to me as if the carburetor isn’t getting enough fuel. I would check all possibilities before either tearing into or replacing a carburetor.


#11

Oh goody goody, a carb question. I’ve rebuilt many a four barrel carb on my Olds, Pontiac, etc. and never had a problem. You allow about 4 hours or more and follow the manual and directions precisely, and cleanliness is absolute.

The accelerator pump is just under the top cover so all that is required is to take the top of the carb off. It doesn’t sound like that is the problem though. The symptoms for a bad acc pump are that it stumbles when accelerating because additional gas is not getting squirted into the intake. Stalling sounds more like a fuel pump, filter or float issue. Most of those used a plastic composition float and over time they would become water logged and not operate properly.


#12

A fellow wacko! I also enjoy rebuilding carbs. But, I do agree that it is a tricky and cautious business, and if you are not a person who is happy fiddling with little parts and working crouched over a smelly bowl of gas and grease and screws and tiny springs and check balls that want to fly across the kitchen, forget it. Buy a rebuilt.


#13

I was one of our dealership’s main carburetor rebuild mechanics. I felt like I could rebuild them in my sleep. That was 30 years ago.

I agree with the cautions shared in this thread. If I were to rebuild an old 4-barrel today, I’d get a good manual and I’d be prepared to go through it very carefully and slowly.

By the way, based on the symptoms the OP described, I believe something other than the accelerator pump is at fault.