Part number for 1987 P30 454 mechanical fuel pump.

[M & J]

I need to know what fuel pump replaces the mechanical pump on our 1987 Allegro P30 454 MH.

I called my friend at a GM parts counter and he gave me  GM 6472478 however that number crosses to various aftermarket pumps all showing as compatible.

The differences are besides hose fittings, the GPM ratings. Some show 25 GPM, and some show 40 GPM. All are rated at 7.5 - 9 PSI.

Sunday morning we were getting ready to leave and the mechanical pump started spitting fuel out. I called around and found a pump in stock for a 1985 K30 1 ton 454 the only one for miles. I drove 50 miles to get that one, got it on and off we went. About 2/3 way home the 454 started backfiring on decel and it got progressively worse (sounded like shotgun blasts with flames out the pipes) until it finally died and would not restart.  Got it towed and later last night I went out and it did start up and ran for about 10 seconds then died again.

I'm thinking that pump has too much fuel flow at 40 GPM but can't confirm because of all the cross references the online searching gives.

Could be a stuck float or carb issue but until I can confirm or deny if the pump I put on is a close enough  replacement, I'd rather not do any more poking around.

The pump I put on was an Airtex  A1108MP. The GM part number 6472478 crosses to a 42440 but again, I see a number of pumps and want to make sure or try to find out if I need a 25 GPM or if a 40 GPM.


Thanks guys.

[legomybago]

This is kinda  a shot in the dark here, but I would think 40 gpm would be if you have a fuel return line (3-port pump) vs a standard 2 port chevy pickup pump which would have the 25 gpm??? I could be wrong i??

At any time did you smell fuel during the back firing issues? Or at anytime?

[M & J]

It is a return style pump. And information like that is exactly what I'm trying to help get sorted before i troubleshoot further.
I was so busy looking at the gauges, watching traffic and my wifey asking excited questions I dont recall smelling gas when it was backfiring. When it died and I manhandled it to the side of the road and lifted the hatch it seems I smelled gas.. I was more concerned if there were smoke and flames at the time. Lol

[legomybago]

Can you get it to back fire now sitting at home in the driveway? Does it only do it when the engine is warm? I dont want to have you searching elsewhere without giving you specs on your fuel pump (Im not really a spec guy!!), but your distributor may be having issues...backfiring is usually timing related. Some more ideas i??

[cncsparky]

I put an ACDelco 42440 pump.  Was warned by several mechanics to stay away from Airtex pumps  i??

[Rickf1985]

I am thinking that maybe you have a coil or ignition module going bad. The fuel pump would not cause backfiring on decelleration.

[M & J]

Sparky. Rick, Legomybago,

It does it hot or cold. While home for lunch i removed the top of the air cleaner, propped open the choke plate and just turn the key on. The electric fuel pump turned on and in a matter of seconds fuel was pouring in to carb on the front venturis. This is not the factory carb but a Holley Truck Avenger the dealer put on years ago and it has served well.
Last year I had a similar issue when pulling up to the house from a trip. Would barely run, backfiring. I did the same thing and fuel was pouring in to the manifold from the rear bowl. Pulled apart, cleaned the float valve and cured the problem.

The back firing this time was massive and I'm surprised there is anything left of mufflers and pipes. There must have been large amounts of raw fuel in the exhaust and again, it only happened on deceleration. When I accelerated the backfiring stopped and I had power - until it died.

I can still order the AC Delco OEM pump through my GM parts buddy for $47. That is the same as the 42440 Sparky has.
It was just odd it ran great after we swapped the pump out for 20 miles then BOOM it sounded like World War 3 when coasting.

I thought about the ignition Rick however when i gave it pedal it pulled smoothly away - didn't miss or cutout or backfire. That's why I was leaning toward a way over rich fuel problem.

Thanks so far guys.

[Rickf1985]

If it is pouring in with the throttle closed then STOP!!!!! Change your oil first thing since it will be full of gas. You are taking a serious chance of hydrolocking the engine. That is chancing a bent rod if you turn it over at the wrong time.

[DaveVA78Chieftain]

Is the regulator for the electric pump adjusted to high blowing out the mechanical pump?  Regulator output should be 4 1/2 to 5 PSI.  Output of mechanical should be 1 1/2 to 5 psi at idle.

Only spec I see for flow is 1/2 pint or more in 15 seconds.  So 4 pints in 60 seconds or 1/2 gallon minimum per minute translates to 30 gallon minimum per hour.  I suggest the 40 gal/hr version.

Dave

[M & J]

I know Rick. Thanks.

[cncsparky]

Fuel should not be coming out of the venturies, either too much pressure or trash in the needle/seat.  The original QJ had a filter at the carb, you might consider putting a fine in line filter. 

[legomybago]

You were close to having a fire!!!

I would check the pressure coming out of your electric pump and regulator to the carb with engine not running, since this has happened before..You even had a fuel leak out of your old mechanical pump? Im seeing a lot of hints here now W%  I think your electric pump or your regulator (if you have one) is putting it's foot to the wood!!

[M & J]

The flooding problem is fixed.

I pulled the front bowl of the Holley Truck Avenger carb and cleaned the float valve. Before I could easily blow through it from the fuel intake. After removing and using some carb cleaner it sealed tight as a drum.

Replaced and fired it up. No over rich condition. No back firing. No blowing fuel down the venturi with just the key running the electric fuel pump. Fixed.

However I do run a fuel pressure gauge and it pulses between 5 - 9 lbs (its not dampened so it shows the mechanical pump pulses). After reading and discussion, i thought it was way over pressure. However after consulting the manual for that carb, it wants 5 - 7 lbs so it's close. I may install a Holley FPR set at 5 - 6 just to smooth out the flow.

Anyway - back on the road. 

[Stripe]

Sweet!
Good to know Betty's on the mend!