Pre-workhorse 454 engine needs help

[DaveFL]

I posted this at RV.net but this group probably has more 454 engine experience.

After reading all 454 gas breakdown posts at RV.net, it seems to be a common occurrence that sensors tell computer to shutdown engine for preservation. Do all sensors record in the computer? Which sensors can be bypassed to keep engine running until it is convenient to repair.

1999 Chevy p32 chassis with 454 7.4L, 32,000 miles, the next year it became a workhorse.

PO changed fuel filters every time he had problem or service and showed me where the spare filter was, I think he was trying to warn me of the possible problem engine has.
After driving it home 50 miles check engine light showed problem with O2 sensor so replaced. I also changed spark plugs, wires(chewed on by field mice or squirrel} also replaced chewed vaccuum lines. First trip of 50 miles no problems second trip of 75 miles a couple of shutdowns.

I am still trying to workout 2 engine shutdowns, NO error codes in the computer, first time after two hours at 55mph, no power coasted to side of road. It restarted after checking all fluids, second time again after two hours of driving but at a traffic light on proceeding into intersection, power was limited, it was running enough to make it though intersection, pulling to side of road, turned off key and restarted, sounded normal so drove last mile to home and parked.

I did get a few good responses at rv.net including ignition switch, corrosion at firewall connections, run obdII while driving monitoring live engine operation. What is the best computer program to send info from obdII to computer for recording?

I still have a few things to try: insulate fuel lines(possible vapor lock), check fuel cap, test fuel pump pressure, confirm vacuum at manifold.
Put on that spare fuel filter ,according to book, filter is only changed every 30,000 miles, but technicians always change when any running problem occurs.

[sknight]

My experience says your fuel pump is giving up the ghost. Check the fuel pressure and see if you can catch it in the act.

During the reduced power did it run smooth, just no power?

[DaveFL]

Quote:

Originally Posted by sknight My experience says your fuel pump is giving up the ghost. Check the fuel pressure and see if you can catch it in the act. During the reduced power did it run smooth, just no power?

Not smooth, the vehicle is so heavy and insulation from engine hard to tell much. Power was too little to continue even at slower speed.

[sknight]

I'm still going to lean towards a fuel pump issue. Usually an ignition problem just quits or runs rough, not just low power. Cheap and dirty way to check for an ignition fault is to hook a timing light up, leave the gun portion visible and watch the strobe. Engine quits and the strobe flashes then the ignition is OK. No flash, now you have a place to start looking.

[Sammie]

I had a similar problem with my 2000 Adventurer with the 454 Engine. Turned out to be a wire shorting out in the main wire loom where it crosses the top of the air conditioning pump bracket. Open up the engine compartment and see if this big loom of wires isn't stretched to tight across the pump bracket. As I recall it was on the left front part of the engine. Maybe you can see it arcing at night.

Sammie

[EngineerMike]

Odd, I coulda sword I hada 1998 P30 Workhorse chassis manual.

Gotta start w/the basics- gas & spark. I'm thinking electrical is at least as likely as fuel. Complete inspection of wiring looms is needed, as well as basic battery cables (corroded, swelled, frayed?), connections (corroded, actually clean & tight not just visually clean and hand tight?), and batteries themselves. Then proceed to more complicated stuff like alternator...

Not sure of the labor req'd to replace fuel pump; my P30 was electric but diesel so gasser might be different. Rig is 11 years old so if the labor isn't ridiculous, changing the pump might be as easy as checking pump pressure if cost isn't ridiculous for the pump.

[DaveFL]

Quote:

Originally Posted by EngineerMike Odd, I coulda sword I hada 1998 P30 Workhorse chassis manual. Gotta start w/the basics- gas & spark. I'm thinking electrical is at least as likely as fuel. Complete inspection of wiring looms is needed, as well as basic battery cables (corroded, swelled, frayed?), connections (corroded, actually clean & tight not just visually clean and hand tight?), and batteries themselves. Then proceed to more complicated stuff like alternator...

Batteries have been replaced, with all connections cleaned, wire looms and frayed wires from squirrels or rubbing a good bet. Also will be checking all grounds by removing, cleaning, applying dielectric and reinstall.
Alternator is putting out, normal.
Workhorse for Airstreams started in 2000 or 2001 depending on stock.
My chevy chassis shows a 98 completion date, Airstream completed build in 1999 and sold it as a 2000.
Do have the wire loom crossing near compressor, checked very carefully and taped open but out of loom wires just before connectors, if it is arcing would only be very short as motor ran both times for two hours without a problem.

[mfire1339]

Check wire connections on oil sending unit. I believe it shuts down fuel pump relay.

Mike

[DaveFL]

Quote:

Originally Posted by mfire1339 Check wire connections on oil sending unit. I believe it shuts down fuel pump relay. Mike

Thanks, I did notice on the first shutdown that the oil gauge was showing zero pressure, when I stopped I checked oil and it was hard to see on dipstick, recent oil change and thin so it didn't fill the holes, took it a second time just to be sure. Could only see by reflecting sunlight off stick.
Dave

[mike brez]

I think the oil pressure switch is a fail safe for the fuel pump relay. If the relay craps out the pressure switch takes over for the relay. You will have a hard starting proplem if the relay goes due to the time it takes cranking the engine to build oil pressure so the pressure switch will start the fuel pump.

[mike brez]

Any head way on your problem. Let us know what you find.

[speed racer]

Your computer has a built in delay that runs the fuel pump untill the engine gets oil presure. If you lose oil pres. the oil pres. switch will shut down the fuel pump to save the engine. Replace the fuel pump relay and the oil press switch for that system. Some of the early models had two one for the oil presure gauge and one for the fuel pump relay.

[DaveFL]

Quote:

Originally Posted by mike brez Any head way on your problem. Let us know what you find.

Changed out rotor, distributor cap and coil, engine wouldn't start put back old ones and got clicking, low battery, vehicle sitting too long and plugged in it doesn't charge start battery, reinstalled new r,cap and coil after charging battery and it started normally.
My new fuel pressure gauge came today so next is to check pressure of fuel before ff change and after, and one more time after blowing line back to tank to see if the screen is clogged. Within the next two weeks it will be time for another test trip.

[DaveFL]

Quote:

Originally Posted by speed racer Your computer has a built in delay that runs the fuel pump untill the engine gets oil presure. If you lose oil pres. the oil pres. switch will shut down the fuel pump to save the engine. Replace the fuel pump relay and the oil press switch for that system. Some of the early models had two one for the oil presure gauge and one for the fuel pump relay.

Thanks, three more things to check or replace.
ECU center of all communication expensive so will save that for last

Oil pressure sending unit, relatively cheap and I did find it under distributor, might even be able to get to it without removing anything.

Fuel Relay should be able to test, on or off by applying 12v. Possible temp fix would be to add a switch to control it directly, might be hard to remember to shut off before or after impact But thinking about it the computer probably would shut it all down if it doesn't get the right signal.
I could wire in an indicator light in parallel showing whether or not voltage is being sent to the fuel pump.