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89 Winnebago Chev 454 Cut-out problem Kim B 7-27-02  
Have an '89 23' Winny w/Chev 454. In hot weather, after an hr or so it starts to cut-out, first on hills, than on level roads, soon barely able to keep it at 35mph or so. Replaced plugs, plug wires, ign. switch, fuel filters, dist. cap, rotor. One mechanic said it was a regulator left on the chassis by mistake in front of the tank and removed it, installing an elec fuel pump in it's place. First happened at half tank when crossing country and prob went away at full tank. Now who knows -- only seems to happen when it's hot out and been on the road for awhile. HELP!
Re: 89 Winnebago Chev 454 Cut-out problem mda 7-1-04  
Had similar problem on 454 in an older motorhome (73) and tried everything suggested - finally, a young kid at a chev dealer in a farm town was wiggling the wires around with the engine running and it died. Turned out it was a simple wire clip that had been squeezed and held by the insulation. just enough wire contact to keep it running, but if a bit of heat expansion was involved (hot day) it somehow broke the contact. This vehicle had an old style distributor - but I'M sure the new style could have the same bad connection.
Re: 89 Winnebago Chev 454 Cut-out problem Robert 7-27-02  
It could be a vapor lock, or a blocked vented gas cap. Does it cut out all of a sudden, or sputters and dies? Is your engine fuel injected or carburated? Does it have electronic ignition? How many miles is on the engine? Does the engine temp gauge show that it's normal, or are you overheating? Also, is it an automatic or stick? This information would be helpful in the diagnosis of your problem.
Re: 89 Winnebago Chev 454 Cut-out problem Vern 7-28-02  
I had a similar problem on my suburban.
Turned out to be the pick-up coil in the bottom of the distributor was opening when hot but worked ok otherwise.
Re: 89 Winnebago Chev 454 Cut-out problem Terry 7-29-02  
Hi,

You may have a fuel vapor lock. Your fuel lines may be near too much heat, and causing the fuel to boil and create gasses that interfer with the fuel pump that is expecting a liquid, and not a gas.
Re: 89 Winnebago Chev 454 Cut-out problem Sam Watson 7-28-02  
Let's see if I've got it right. Runs great for an hour or so after cold start? All the time, or does problem occur sooner if outside temp is high? How long does it take after engine shut off for a restart and normal engine operation ? Engine is mis-firing and running on fewer and fewer cylinders until you can't make over 25-35 MPH on the flats? Fill me in, please
Re: 89 Winnebago Chev 454 Cut-out problem bill h 7-28-02  
How about hooking up a fuel pressure gauge for your next trip?
Re: 89 Winnebago Chev 454 Cut-out problem Kim B 7-28-02  
Thanks for the responses -- add'l info: It typically begins all of the sudden, continuing intermittantly but progressively gets worse: i.e. once it begins, it becomes increasingly impossible to keep it at a steady speed dropping down to 25-35mph. It's carburated and has 31k miles. Temp gauge climbs to the higher range of normal (sometimes it's hot enuf to kick on the clutch fan). It's an automatic.
Re: 89 Winnebago Chev 454 Cut-out problem Joe 7-28-02  
Look for hidden filters. Sometimes there will be a filter just after the line comes out of the tank directly on top of the tank. It is so hidden that sometimes all you can do is feel for them and they are harder yet to change. A fuel pressure gauge may be helpful.
Re: 89 Winnebago Chev 454 Cut-out problem Robert 7-28-02  
An engine needs the proper amount of fuel, air, spark and compression, and in specific order and duration in order for it to operate properly.

The increase in operating temp probably is cause by the problem you're having, rather than is the cause, and therefore, most likely your problem is not due to overheating. And, since the engine continues to run, albeit lacking power, means that you're getting spark (although, Vern's idea of the pick-up coil might be the culprit - you can have the coil tested before replacing it). I am assuming that the engine's ignition and valve timing is correct, since it runs OK at the start and for some time before the problem occurs, and your engine has low milage. This leads me to believe that you might have a fuel delivery related problem.

You'd mentioned that the fuel filter was changed. Was this the small filter element at the carburator, or was this the main fuel filter underneath the truck? The main fuel filter is usually an inline canister type filter (looks very much like a half of a beer can), which is installed inline with the fuel lines somewhere between the fuel tank and the carburator. Most often, the smaller fuel filter element (about 1/2 inch diameter x 3/4" long, pleated element) at the end of the fuel line that goes into the carburator gets changed, but the main fuel filter is overlooked, since it is usually located underneath the truck along the inside of the frame rails (usually on the driver's side at mid-ship). We have a '94 Suburban, which at around 40k miles, started to loose power. At the time we changed all the tune-up items, including spark wires, had the fuel injectors cleaned, and changed the small fuel filter element at the throttle body, but still the problem got worst. I finally found the main fuel filter underneath the truck (sort of hidden) and changed it. It made all the difference. Now I change this filter every 5k or 6k miles (with every other oil change), and have not had any problems ever since. Hope this is the cause in your case. If not, you might try to trace the fuel lines to make sure they are not obstructed, or has other fuel filters/regulators attached as Joe mentioned. Also, if your gas cap is a vented design, the vents may be clogged. This can sometimes shut down the engine as well.

To check if you're getting the right amount of fuel, disconnect the power connectors going to the distributor-ignition coil. Disconnect the fuel line to the carb, and place it in a large, tall, non-breakable cup. Have someone turn on the ignition key (but no need to crank over the engine since you have an electric fuel pump), and listen for the fuel pump coming on. Be sure and cover the cup and fuel line with a rag (and hold it) to prevent gas from shooting/spilling all over (you'd be amazed how much fuel will shoot out!). If fuel is spilled, stop immediately and clean up before continuing. Measure the amount of fuel in the cup, and compare it with the fuel pump's specs. This will tell you if you're getting the right amount of fuel to the carb, and you can work from there to troubleshoot your problem. Make sure you reconnect the fuel line properly, and clean up all spilled fuel before starting your engine. Don't reuse the fuel in the cup, and please BE VERY CAREFUL AS GASOLINE IS HIGHLY FLAMMABLE AND EXPLOSIVE.

Hope this works out for you. Good luck.
Re: 89 Winnebago Chev 454 Cut-out problem Joe 7-28-02  
The other question I have for you is "Does your motorhome have one tank or two?" I'm assuming one. If you have checked for all possible filters and regulaters, pinched lines, kinked lines, lines too close to the exhaust, then there are other possibilities. A crack in the pick up line in the tank?? Loose line on the pick up on the tank??? You could have a bad fuel pump on the engine itself. Even though you have an electric pump, if the main pump is failing, it is very hard for the electric pump to push the fuel through the main pump sometimes. I have seen this happen. Test the main pump. The next best test will be to install a fuel gauge and drive the unit until the problem shows. When it acts up look at the fuel pressure gauge and see where the pressure is. Then if it is low, and you can safely go out and remove the gas cap and see if it has vacuum or pressure or neither. Don't do it with a lit cigarette in your hand. The other culprit could be the float. This happened to me some years ago on a Cabana with a 454 on a Saturday night in Conway South Carolina. It drove me nuts until I figured it out. When it got hot the composite float swelled enough to stick in the up position and the power just seemed to fade away. With a full tank (and maybe cooler fuel) the problem went away. I bent the float to a new position and it never happened again. Now between myself and others you have many suggestions on how to solve your problem. Try the cheapest first.....do a lot of looking!!!
Reply to Sam re Chev 454 Cut-out problem Kim B 7-28-02  
Hello Sam, thanks for the help. Yes, it seems to run fine for an 1-1.5 hrs after a cold start, at least that was my recent experience. Coinciding factors seem to be outside temp (around 75+ degrees), running for an hour or so, so the engine is hot, and the first cut-out begins when I'm climbing a long hill or mtn (I'm in Oregon). Then it's all downhill fast, literally w/in a few miles. I've never timed a restart back to normal operation -- overnight is best I can think of. As you can tell, I've replaced a lot of parts -- wondering about vapor lock?
Thanks again for the response and your ideas.
Kim
Re: Reply to Sam re Chev 454 Cut-out problem rick 7-28-02  
I have a 1990 bounder with a 454 tbi, had a stalling problem turned out to be a oil pressure switch, that also controlled the signal for the fuel pump relay. the switch was defective and sending a signal to the fuel relay that there was no oil pressure therfore it would shut down the fuel
Re: Reply to Sam re Chev 454 Cut-out problem Sam Watson 7-29-02  
The first thing to determine is if it's a fuel or ignition problem. Let's do the fuel first. With the engine cold, remove the lid of the air cleaner. Look down into the air cleaner to the carburetor air intake, use a mirror if you need to. You'll see that there are two sections of the air intake, or "air horn" as it is called, a large side with a large, pivoted plate closing the opening, (secondary side), and a side with smaller openings, again covered by a pivoted plate, (primary side). The plate at the primary side is the choke blade and is used to enrich the fuel mixture during cold starts. If you look to the rear of the primary section, you'll see a vertical tube sticking up out of the surface of the air horn, that's the bowl vent tube. The bowl vent tube is directly over the carburetor fuel level control float, (works just like a toilet bowl float system). Having identified the parts, we can now make a simple float position gauge. Go to a good hardware store and buy a 1/8" thick brass rod, (they come in 3 foot lengths), cut the rod as needed so you can slip it down the air cleaner and into the bowl vent tube while still holding the other end of it, CAREFULLY slide the rod down into the vent tube until you feel a slight resistance, you've reached the top of the float, STOP. ACCURATELY mark this measurement on the rod, either at the top of the bowl vent tube, or some other accurate index point, as this will be your detection instrument. The next time the problem occurs, get the rig over to the side of the road on as flat a surface as possible, remove the air cleaner lid, and measure the float level. If there is no difference in height from your index mark, then you don't have a fuel problem, but rather an ignition problem.
Re: Reply to Sam re Chev 454 Cut-out problem Barb 11-18-03  
I have same problem with 1978 Chevy 400 engine on a very low mileage Class C given to me by my parents. It also has a NEW fuel pump, and both filters, new spark plugs and wires, rebuilt transmission, distributor, PVC valve. It also has an electric fuel pump installed by first owner, but we're not even sure how or when you use it! Problem has our very good Chevy mechanic stumped! Happens just as described, after running for about one hour or so, even in cooler weather, on steep inclines. As you keep going, it gets worse and worse until it hardly goes up a moderate incline. We need help, what to check first, second?
Re: Reply to Sam re Chev 454 Cut-out problem CHARLES WALLER 7-20-03  
I have the same problem with my 88 Winnebago. It appears to be vaporlock.
My Onan generator quits at + 95 degree
temps as well as the engine.
My 454 quit completely yesterday. After sitting a half hour it would not start.
I removed the air cleaner and the accer.
pump had no gas. I primed the carb with
a little gas and it started immediately.
The only fuel pump is the engine pump.
When I removed the fuel cap the gas seemed to be boiling. I had filled the tanks at
a station that had 10% ethynol added to their gas. I think that exagerated the vapor lock problem.
I hope this info helps someone. Does anyone know if adding some diesel would help wit the vaporlock problem?
Re: Reply to Sam re Chev 454 Cut-out problem Joe 7-29-02  
Sam, that is provided the same problem doesn't exist that I had with a float rubbing on the float bowl and sticking in the closed position.
Re: Reply to Sam re Chev 454 Cut-out problem Sam Watson 7-30-02  
That would be a mis-aligned float, and shouldn't be heat sensative. What we're attempting to do here is narrow the problem down to what system is at fault.
Re: Reply to Sam re Chev 454 Cut-out problem Joe 7-30-02  
I'm well aware of the goal here. And I have had a GM composite float stick when hot. Mopars changed floats because they swelled when they got hot. Going on the fact the problem is worse on a half tank of fuel as opposed to a full tank makes us believe it is fuel related, not ignition.
Re: Reply to Sam re Chev 454 Cut-out problem Sam Watson 7-30-02  
Joe, let's find out for sure using the test rod. Since an electric pump is installed, pulling over to the side on a flat surface, turning engine off, then turning key back on and then GENTLY pushing down on float will, (if stuck at top), allow the bowl to fill, or (if not stuck at top), cause some overflowing of gasolene into carb. The amount of time involved for either to occur will tell if the float was stuck or not.If the float is sticking,then unsticking it should allow the engine to operate correctly for a period of time, right? If normal operation returns, then the cause has been found and carb repair is in order. In my long experience as a Mech Tech, I found that the best approach to solving a problem is to use an analytical approach. "Shotgunning" is hard on the customer's wallet, we both know that in most shops, what's installed doesn't always come back off.
Re: Reply to Sam re Chev 454 Cut-out problem Joe 7-30-02  
That's true, and that is why my advice was "Try the Cheapest thing first...Do a lot of looking." I have been doing this kind of work since 1963 and I could fill several railroad cars full of parts that I have seen replaced that didn't solve the problem.
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