454 Engine feels like its running out of gas

BrianB · June 30, 2016, 11:38 PM

Guys, I'm hoping someone has the answer for me. I'm in middle of nowhere Montana and have an issue with engine feeling like its running out of fuel... no power and acts like stalling when trying to accelerate or go up a hill.

Issue started around Chicago. Been fighting it since and it's worse... almost can't drive at all.

What I've done (before trip):
1. Dropped tanks and cleaned them.
2. All new rubber lines and clamps. Fittings cleaned.
3. New filters between tanks and selector valve.
4. New selector valve.
5. All new return and vent canister lines.

Started hesistating in Chicago. Had hard time making it through Wisconsin to Minnesota border where my family is. Changed the fuel filter in the carb and along the frame rail.

Ran fine for first 60 or so miles then started acting up. Very slow and hard drive to Rapid City SD.

Changed mechanical fuel pump with new one from Napa.

Today ran fine for 60 or 70 miles then started same thing again.

Stopped at top of a pass and cooled off. Bypassed selector valve with a piece of fuel line I had. No improvement.

Stopped at next chainup area and removed doghouse, breather cover and filter. Started engine and pressed the gas a few times then shut off.

Could hear gurgling in the carb.

Ran with cover off and doghouse off and seemed to run fine for about 5 or 6 miles. Tried putting cover on and problems came back. Tried running with doghouse on and cover off. Problems still there.

I am thinking because of the gurgling noise it might be vapor lock. Not sure the easiest way to fix that but need to figure this out ASAP before we head much further towards Alaska.

I will be much obliged to any help any of you can offer.

tmsnyder · July 01, 2016, 07:35 AM

It may be your in-tank electric fuel pump. There's a way to jumper the relay that sends power to the pump, so you can run it without the vehicle running. Or you can do what I did which was to start the engine, then loosen the hose clamp on the pump side of the fuel filter which is on the frame. Without actually removing the fuel line, you will see that it will start squirting gas. If it does, push it back on and clamp it b/c the pump is working. If you end up pulling the line off, the engine is still running, and no fuel is coming from the tank then your pump isn't running. The engine has to be running for that pump to work btw, unless you do the jumper thing. You should also put someone on the key to shut off the engine if you happen to not be able to get the fuel line back on and it's spraying gas all over, unlikely though b/c it's low pressure on these old ones.

If the pump's not running, it doesn't mean the pump is bad. It could be the fuse, the relay, or the oil pressure switch. I believe the fuse and the oil pressure switch are in the area of the drivers side of the engine, and the relay is near the drivers feet. Mine was on the firewall behind the left headlight. It was nicely labeled in fact by HRC.

Good luck

Rickf1985 · July 01, 2016, 09:10 AM

You could be pulling air into the line from a loose connection somewhere if you do not have the electric pump in the tank. If you do have the electric pump and it is working then any loose fittings would be leaking and not causing this problem. Do both tanks have electric pumps? Does the problem exist and to the same degree on both tanks? If it does and the rear tank has an electric pump see if it is working and if it is then the problem is either a clogged filter or it is not fuel related. It could be ignition related, it could possibly be a bad ignition coil. I do not see many bad HEI coils but you are describing the symptoms of a bad coil. Could very easily be a bad ignition module also. The gas bubbling in the carb when shut off does not really mean anything, the engine is hot so it is going to bubble. Vapor lock occurs in the lines, not in the carb. If that is the original ignition module I would try that or at least get one to carry with you. Be sure you get the special compound for between the module and the distributor.

Schwarzkopf9 · July 02, 2016, 05:23 PM

Any possibility of mixing up the fuel supply and return lines? Stranger things have happened...

Rickf1985 · July 02, 2016, 05:27 PM

They should be different sizes. If your generator has it's own line then the return line ends above the gas level so if they were reversed it would stall pretty quickly and not start again. The ones with the generator line tee'd into the return line are a different story as they go down to the 3/4 point in the tank but still are a different size than the supply line. The supply line should be 3/8" I believe and the return is probably 1/4".

Schwarzkopf9 · July 02, 2016, 06:41 PM

Yeah, now that I think on it, you're right.

BrianB · July 02, 2016, 10:27 PM

I really think it is fuel. Running with the air cleaner off and dog house off made a difference.

I bought some 2000 degree reflective thermoshield yesterday in Billings. Going to put that on in the morning before we pull out of Glacier. We'll see if that helps.

When it stalls on the steep grades, I have to crank it a couple of times before the accelerator pumps squirt fuel in. So pretty sure float bowl is empty.

My setup is:
70 gallon main tank with in-tank pump.
30 gallon aux tank with no pump
Main tank has new Holley regulator.
New selector valve.
It's all plumbed correctly.
Genny T's off the 1/4 return line above the differential. Valve at generator is closed.

It won't run off the aux tank for more than 20 miles, but then runs fine if I switch to main tank. This until the engine gets hot. Yet another indication (switching tanks) that it is fuel related. Also, stopping for 5 minutes to fill up results in it running a little better for about 10 miles (cold fuel load?) My brother says that the return fuel heats the tank and could be a contributing factor.

There's no parts store between here and Canada, so if it acts up I'll have to try to nurse it to Calgary.

Rickf1985 · July 03, 2016, 11:28 AM

It sounds to me like your mechanical fuel pump is bad. I know you said you replaced it but I have seen more bad ones our of the box than off of the engine in the last few years, Chinese specials. Without checking fuel pressure everything you do from here on out is speculation and you are just throwing parts at it hoping for the best. That is not a good plan or diagnostic procedure. You need to pin down the problem using tools, not guesswork before you get to a point where you need to be towed hundreds of miles! It does sound fuel related but you need to know what part of the system to change and unfortunately you cannot go buy the old fashioned ways of 'Well I already replaced the pump so it can't be that", Well, it can be. With the gas boiling in the carburetor one of the things I would look at and as a matter of fact I would be sure it is disconnect and wide open is the heat riser valve on the exhaust manifold. On most it is on the drivers side at the exit of the manifold and will have a vacuum tube coming up to the the engine ending next to the carburetor. Disconnect and plug that vacuum line and make sure you are getting equal exhaust flow out of both exhaust pipes. When that valve is closed it routes exhaust gas from the left side up through the intake manifold and over to the right side and then out. This is controlled by the TVS on the thermostat housing. As the water temp comes up it is supposed to open that valve but I have seen many stuck valves. It is not needed on a motor home since it is unlikely you are going to just start and run on a very cold day anyway. The engine will still warm up pretty quickly.

BrianB · July 04, 2016, 09:27 AM

Thanks for the suggestions Rick. I am now positive it's not the ignition coil. Got one of those and installed at Calgary. Ran the same pulling out of there.

I am in Edmonton waiting for places to open. Fortunately the Walmart here has free WiFi.

It is definitely temperature related. We ran into a cold air mass and rain from Calgary north and it ran a lot better. I was able to keep up with traffic. But got worse again later when we drove out of that.

I had checked the exhaust valve (was able to operate it by sucking on the tube) when I had everything apart. But your point is valid I supose. I do know there is exhaust coming out of both tubes.

I've really been trying to avoid replacing carb. But if I have to, is there something that is bolt-on and easily available?

Any other tips welcome....

Rickf1985 · July 04, 2016, 10:24 AM

The only thing you are going to find that is a bolt on direct carb is another quadrajet. You may find one in one of the parts stores but they are going to want yours as a core and you have no idea of the condition of the rebuild you are going to get. You are probably going to pay upwards of 3 hundred for it when you could get hold of Sean Murphy in Ca. and get one of his custom rebuilds for the same price. At least then you know you have a quality carb. Or if you can find a Summit dealer in your travels you could pick up a Edelbrock 750 CFM Performer carb but you will need an adapter which may make your air cleaner to high under the dogbox. The Edelbrock carburetor number is a 1411.

There will always be exhaust coming out of both pipes but it should be equal, the valve blocks off about half of it. If you know the valve opens and closes then it is probably open. Pull the vacuum line of and plug it to be sure, you do not need it. Timing is done from underneath on the drivers side with the timing light hooked to #5 plug. Original spec is 4 degrees BTDC, I was running 10 BTDC and full manifold vacuum on the vacuum advance and I was getting just a tiny bit of pinging at 60 MPH. I would suggest to you to set the base timing with the vacuum advance off at at least 6-8 BTDC. You can try running the vacuum advance on manifold vacuum but since you are on the road I would say just leave it as is for now and play with it later when you get to where you are going. If your timing is 4 BTDC or less that will cause it to run hot at idle if the vacuum advance is set to ported vacuum. We are sort of crossing into a different set of posts here but this is still related to your heat issue. If you want to further discuss the timing issue lets do that by pm for now, otherwise we can continue with the other stuff as we were.

bluebird · July 04, 2016, 12:06 PM

Changing the carb won't stop the boiling of the fuel in it. Have you tried insulating the fuel line from the pump to the carb? You need be make sure you have the correct fuel pressure to keep the fuel bowl full. What pressure did you set your regulator to? Does the tank pump work? I wouldn't use the original carb for a trade in if you decide to replace it.

By the way running the engine lean is causing more heat making things worse. You could be on the verge of burning pistons, destroying the engine.

BrianB · July 04, 2016, 05:34 PM

I did try insulating the fuel line (mentioned in prior post) but it did not help.

I found a classic car shop here that is going to look at it. Hope to be on the road again by tomorrow.

Rickf1985 · July 04, 2016, 06:05 PM

They should have the smarts to rebuild your carb if needed and also know the timing tricks.

cook elandan · July 05, 2016, 02:05 PM

If it were me, I would start with simple. by-pass the selector valve and hook up the Aux tank only. Make sure it has at least 1/2 tank of gas. If your fuel pump is good then you should be getting fuel to the carb. Just to make sure, you said you put on a new fuel pump, the pump rod did not fall out and it is missing?
Is the carb filling with fuel and maintaining fuel. You said you change the carb fuel filter. Make sure it was the same size and installed in the correct direction?
If all ok here. then the engine should be running and maintaining fuel in the carb. You could check by disconnecting fuel line from carb and place line into a container, crank the motor and make sure the the pump is flowing fuel.
You said that it ran better with dog house open or when the weather was cooler. Are there any obstructions in the front , clogged radiator , cooling fans working?
JMO on my thinking and how i would go about it. Get it working this way and then tackle the rear tank.

JerryP · July 05, 2016, 03:39 PM

I would be checking the ignition, especially the coil, and plug wires.
I have had the same weird intermittent issues with failing coils, and plug wires.
Coil heats up, begins to act silly, cools down, runs fine, then it does not.
Plugs wires exposed to heat around the exhaust sometimes act weird when they have been exposed to heat too much, and short out.
Had a Fiero that I had to change the plug wires every year, due to the heat under the hood. The Car ran flawless, other than that.

Coils, and plugs when failing can seem like fuel issues

Rickf1985 · July 05, 2016, 06:09 PM

Replaced coil, reply #8

BrianB · July 06, 2016, 12:25 PM

Running better now. Electric pump in tank not.working. New electric on frame rail. Choke was sticking too and high idle and dieseling fixed.

We'll see. Ran much better yesterday.

All the ignition was new before I left except the coil and bite that's new as well.

legomybago · July 06, 2016, 12:59 PM

P30 454 chassis rigs HAVE to have an electric fuel pump these days to prevent vapor lock due to the fuel that "they" sell us today.....

shortbus · July 06, 2016, 01:47 PM

Quote from: legomybago on July 06, 2016, 12:59 PM
P30 454 chassis rigs HAVE to have an electric fuel pump these days to prevent vapor lock due to the fuel that "they" sell us today.....

After a year and 18k miles or so I have had no real problems on mine with just the mechanical pump on the engine, but at only 23ft long. It doesn't have all too far to go.

legomybago · July 06, 2016, 01:59 PM

Your 87' should have an electric pump? Maybe it slipped through the cracks at the factory i??

shortbus · July 06, 2016, 03:39 PM

I've discussed it before on another thread. Being an 87 yes it should, but our theory was they just left it out of the short one because it wasn't really necessary. I mean, my wheelbase is shorter than most pickup trucks. Did the 87 2500 w/ a 454 have an in tank pump, or was the pickup already on TBI at that point?

legomybago · July 06, 2016, 05:56 PM

The Sub and pickup 454's were TBI then so I read.
Our 86' P30 ran good without the electric pump option 5 years ago when we first purchased it, then we started having vapor lock issues about 3 or so years ago. Went through the entire fuel system to verify correct, then installed an electric Holley pump. Runs like a dream climbing hills in 100* weather now. I sometimes will run it just on the mechanical pump, and it will do pretty good for a bit, but when you stop and fill the gas tank, then fire it up to head out, you are almost guaranteed vapor lock after heat soak.

Rickf1985 · July 06, 2016, 06:58 PM

As long as you do not have the monstrous 1/2" fuel line then a engine mounted pump will work fine on the shorter vehicles. On the really long ones if you have 3/8" line you may get by and 5/16 you will have no issues pulling fuel but getting enough fuel through that size line would be an issue. Once they went to the electric pump in the tank they went to 1/2" line and there is no way in hell you can pull from the tank with the engine mounted pump with that, too much air to absorb the vacuum before you can lift the fuel. Once the line is completely full of fuel with no air in it then you could do it but one big bubble hitting the pump and you are done.

legomybago · July 07, 2016, 11:32 AM

Our 1985 chassis has the 1/2" supply line with mechanical fuel pump only from the factory. So at one time this system was good/ok other than the time it still took to prime the carb on cold start after setting. Who knows..... i??

BrianB · July 17, 2016, 05:27 PM

This still isn't solved... Ugh.

Had trouble from Whitehorse to Dawson City. Was able to make it up the Top of the World and into Tok.

However getting to Fairbanks it was progressively worse.

In Fairbanks, tried moving the electric pump installed at Edmonton from along the front frame rail to back right above the fuel selector valve. No good. Couldn't get up the hill heading out of Fairbanks.

I took the car and went back to town and got a new electric pump (an SP8012, 5-9 psi) and put that on. Worked great - for about 20 miles, then it quit. Side of the road. Made to a spot I could pull off the highway fully. No pulsing on the pump. Voltage 12V when unhooked, 9 volts when hooked to pump. Took it off and back to Fairbanks in the car. No one had another SP8012 punp, so had to buy the only SP8016 (2.5 - 5 psi) pump. Back to the RV to install. Ran great for 30 miles then started behaving same again.

My setup is 2 tanks, through filters, through selector valve, to electric pump mounted right between the tanks. Then up the 1/2" line to the mechanical pump then to the engine.

It iw wired through a relay and 30A fuse, control for relay is the electric choke wire which is controlled by a oil pressure switch.

Not sure how I can be burning through pumps or if something else to causing this. This last time I was running on aux tank, so not pulling through broken electric pump in main tank.

Ideas? I'm at Denali and told there is a Carquest nearby, but not sure what they have in terms of parts yet...