Chevy 454 Problems PLEASE HELP!!!

[casualrver]

Sorry if there is a thread for this but I could not find one that really helped me out.

Here is the problem I am having:

I have a 1986 pace arrow. It has a new rebuilt Chevy 454 in it (rebuilt last year). The motor home will start just fine, but after about a 1/4 mile down the road it will die. We thought it might have been the fuel filters so we replaced both of them. Then we thought it might have been the inline fuel pump but that checked out ok. So we looked at the distributor and ignition module. The ignition module had some burn marks around the outside of magnet so we replaced it. Starts right up with no problem. We took it out on a test drive and it died about 1/4 mile down the road again. After it dies we can't get it back started again and the starter acts like it is really working hard to turn the motor.

I have been trying to wrap my head around this problem and can't get this thing figured out. I would really appreciate some help.

I am thinking maybe a clogged catalytic converter? What do you guys think?

Thanks in advance for the help!!!

[Jayco23FB]

The first thing to do is see if you have spark when it dies. If there is no spark it may be the HEI module. As for the starter turning over hard check to see if the centrifugal advance is seized in full advance. (check by turning the dist rotor, it should move in one direction and spring back into it's normal position if it is ok. If it doesn't pull the dist and repair the shaft. I doubt you have a vapor lock issue as 1/4 mile would not create enough heat. Another thing to look at is the ignition coil. Light gray marks around the laminated bracket indicate coil tracking. If found replace the coil. Also make sure that the ground strap is in place. This is a small angular piece of metal that grounds the coil and is connected to one of the 4 coil mounting screws. It is often left off and can cause the coil to track. I am not sure what you mean by the ignition module having burn marks by the magnet that doesn't make sense to me. It is very common for mechanics to forget to put the ground bracket back on when changing or repairing ignition systems. All this said I am assuming you have a 1986 7.4 with HEI ignition and a four barrel quadrajet carb. My recommendation is see if you have spark when it dies it will save you a lot of time. (22 years as a GM mech.)Good luck.

[Dannyabear1]

If it is carberated, there is a small bronze filter in the carb. that could be plugged up.

[msgross]

good tip with trying to start it with starter fluid after it dies. Could be any of these issues, tank not breathing right and causing a vacuum lock is my first guess. Choke on card is a good thought as well...

Start simple and rule out those issues. Fuel, spark and air is all they need to run.

[Dog_Folks]

Lots of suggestions offered.

Please let us know what you find.

[Coyote74]

A thing I just remembered happen to me. The choke closed manually, but as the engine warmed it choked fully a cut engine off. It would not start until choke was opened manually. The electric choke unit lost its voltage. It requires 12 volt to keep it off. It must be constant 12v.

[enblethen]

I would look into the carb. The float could be sticking, closing the fuel off from getting to the bowl.

[BrianinMichigan]

Look for leaking gas around the rear by the gas tank. Sounds like a cracked fuel line. Put a pressure gauge on the fuel line near the carburetor and keep an eye on the pressure while your driving. Should be around 7 lbs of pressure.

[2bzy2c]

Here is how to check if it is fuel related or ignition related.

Go to an auto parts store and get a can of starting fluid. Take your RV out and when it dies, try starting it while spraying the starter fluid into the carb. If it runs for a moment, you know its fuel related. If there is no difference and the RV does not start, then you know it is ignition related.

NOTE- Only spray and use the starter fluid once or twice. More than that could damage the engine. Use it only for diagnostics. Your engine will only run for a few seconds and it will knock and ping like crazy. But if it does run, look to a fuel issue as mentioned in previous posts.

[More_To_See]

Does it die suddenly like somebody turned off the key (an electrical problem) or sort of "mush out" like fuel starvation or something else?

[turbojimmy]

I would bypass the electric pump to eliminate that as a cause. The pump is only there to solve vapor lock issues. Someone removed the electric pump from my '84 in the past and it runs fine without it.

If the pumps are working okay, I would suspect deteriorated lines between the tank and the solid steel fuel line. The pump(s) will lose their prime if there are air leaks. I had this problem on my '84. The generator would run for a while but would eventually run out of gas. The engine eventually wouldn't run at all.

The fuel lines should be easily accessible on the RH frame rail by the tank. A good test is to dip a line into a container of fuel right off of the frame-rail-mounted line. This bypasses the rubber hoses that run atop the tank.

[Sully2]

Make sure the fuel pump RELAY is working 100%.

[ScottG]

Suburbans of that era would loose both the fuel pump and its relay and cause the starvation symptoms you have. Might be cheap insurance to replace the relay now.

[Born_To_Travel]

Remove the starter and have it load tested at an auto parts store.. Chevys for years have had a problem with engine heat on the starter motor/solenoid and when they go bad you will have a problem as you describe... If it turns over hard after it happens, But starts fine after a half hour or so, I would pull it off and have it checked...

[Executive45]

It's an 86 so no crankshaft sensor.

From your description it sounds like you are having a fuel starvation issue. The coach starts up and runs when it's cold but stalls after it warms up. Several things come to mind.

First is routing of your fuel lines. Make sure they're no where near your exhaust manifolds or any heat source. Wrap them if necessary.
Second..are you using rubber fuel lines or steel? Rubber will collapse under hard throttle in certain circumstances.
Third..are you using an electric or manual fuel pump?
Fourth..after it stalls, remove the air cleaner (if its on) and check the butterflies in the carb. Often, after the engine warms up, the spring that holds the butterflies in place is weak and the butterflies will close under throttle. This provides too rich a mixture and will cause the motor to stall. An easy test is to warm the engine, then wire the butterflies open and drive it. See if it stalls. If not, your problem is in the carb.

I don't see it being an exhaust issue as you would experience that without driving the coach.

Try to eliminate the fuel delivery problem. Once that's proven not to be the issue, let us know and we can try some electrical things. My guess is one of the above will be the culprit....with the carb my number one guess....Dennis