76’ MInnie - Gas Pedal giving out at high speeds. Fuel Pump?

[phillipsac]

Hey there!

I’m midway through a trip from NC to CO in my 76’ Minnie Winnie. The gas pedal has puttered out on me a few times over the last few days while going around 60/70mph. One time so much so it came to a full stop on the side of the road but recovered.

This same thing happened before while going up a mountain, and A friend mentioned to me that maybe I should keep the tank more full because the fuel pump might be struggling.

I’ve now been keeping it above half tank and mostly avoiding the issue, but it still putters occasionally and slows me down to 40/50mph for a little while - even around 3/4 full tank.

Is this a manageable solution? Or is this going to strand me on the side of the road in the next day or so of travel?

Anything else I can do to aid my poor RV? Do I need a big repair? (I just got done dropping 3K on new brakes and shocks so I’m definitely trying to avoid the expense.

Any help is very much appreciated! I’m still out here cruising!

[Goodspike]

Could also be fuel filter.

I'm not sure if modern vehicles still get vapor lock, but your description sounds a lot like that. Was it particularly hot weather when this happened? Had you been driving for several hours?

Edit: I just saw 1976. My guess is vapor lock if the answer to one or both of those questions is yes.

[phillipsac]

It wasn’t that hot out, maybe high 80s?

And when it happened before on an incline it was definitely pretty hot out.

[MinntoMich]

This is a mechanical fuel pump, not electric right?

70 MPH in a 1976 with a 3 speed automatic... That motor must be roaring.

[Goodspike]

Originally Posted by phillipsac

It wasn’t that hot out, maybe high 80s?

And when it happened before on an incline it was definitely pretty hot out.

I would call high 80s hot. Note I edited to ask how long you'd been driving too. Also impacting it would be speed and grade--basically how hard is the engine working and how hot are things getting.

[Goodspike]

Note: It should also be fairly easy/inexpensive to change the fuel filter on a 1976 vehicle. If you haven't done that for a while, or don't even know how old the filter is, I would start there. You can even get some idea how restricted the old filter was once it's removed.

[Winterbagoal]

Assuming you mean "sputters", not golf clubs, Goodspike's theories sound plausible.
Any idea what chassis year/make/model it is? Is it carbureted or fuel injected? Someone on here will probably know right away where your filter or fuel pump is located, based on that info.
Depending on the location of the fuel filter it could be a simple DIY, if it's located along the fuel line from the tank to the carb/injectors. If it's an electric fuel pump it will be a little more pricey if it's inside the tank, if the tank has to be dropped to get to it. Otherwise, some low pressure pumps are closer to the carb/injectors and are driven mechanically.

If it turns out to be the fuel pump, get the filter changed at the same time.

[Goodspike]

I would think a 1976 would be a carb with a mechanical fuel pump.

I'm not certain of this, but I think modern systems use a higher pressure and also push rather than pull the fuel from the tank. They may also recirculate the fuel back to the tank. That makes a vapor lock much less likely in modern vehicles--I think.

[Winterbagoal]

Originally Posted by MinntoMich

This is a mechanical fuel pump, not electric right?

70 MPH in a 1976 with a 3 speed automatic... That motor must be roaring.

70 MPH in a 2020 with either a 7.3L V8 or 6.8L V10...same result, especially up hills. Been there, heard that.

[Winterbagoal]

Originally Posted by Goodspike

I would think a 1976 would be a carb with a mechanical fuel pump.

I'm not certain of this, but I think modern systems use a higher pressure and also push rather than pull the fuel from the tank. They may also recirculate the fuel back to the tank. That makes a vapor lock much less likely in modern vehicles--I think.

Trying to remember when they cut over to all fuel injected, on Fords (probably) around that time, on certain chassis. If it's a carbureted engine, probably mechanical pump, if FI, probably electric, possibly inside the tank. I had a 1978 E150 Econoline with the 351 V8, and I can't remember which it was.
Need more info.
Found a thread about a '79 F150, dude wants to replace his mechanical with an electric, so I'm thinking maybe OP has a mechanical pump inside the engine compartment, in a '76 anything.

[Goodspike]

Knowing carburetor or fuel injection would help. I'm not familiar with early fuel injection systems, such as what type of fuel pumps they used. I think my first FI vehicle was a 1986.

I do know they existed in 1976, because I remember a Honda Engineer talking about their CVCC engines and how fuel injecting the smaller richer chamber would be difficult. Those CVCC engines were about 1974-76.

[phillipsac]

Thank you all so much for the help!

It’s carbureted, it’s a Holley 2-Barrel.

It’s a 76 Minnie Winnie 26RB on a Dodge Tradesman. I was told maybe C300?

[MinntoMich]

Originally Posted by phillipsac

Thank you all so much for the help!

It’s carbureted, it’s a Holley 2-Barrel.

It’s a 76 Minnie Winnie 26RB on a Dodge Tradesman. I was told maybe C300?

All other things being equal my guess is that Goodspike is correct, start with the simplest and easiest fix, the fuel filter. If you have a 2bbl carb on a Dodge then it must be a 360 I'm guessing. It should be located somewhere on the passenger side frame about 1/3 way down from the front end.

The reason I'm asking if the pump is electric or mechanical is sometimes folks retrofit them. The electric aftermarket will draw more fuel than the stock mechanical and can create a vacuum/draw problem in the gas tank.

My experience with running my 76' in hot weather was in traffic. It got so hot the motor stopped. I'm guessing it was vapor lock. If the motor is way hot giving how close the fuel lines are to the block that does make some sense.

Sometimes failing ignition or electrical problems (plug wires, coil, electronic ignition control module) can show up when its hot.

I think its an MB300. That's what mine was. No difference though. Its on a 3/4 ton chassis and Chrysler did make them tough then.

Plese keep us posted.

Edit... Just a thought.... Could you have gotten some bad gas? A little water or to much ethanol? I'm sure at 7 MPG your gonna fill up soon and know if a fresh tank makes a difference or not.

[Goodspike]

Okay, given it's a carb setup I'll stand by my two positions. Possible vapor lock, but change the fuel filter if you don't know how old it is, etc.

BTW, I'm not 100% sure of this explanation, but basically what I think vapor lock is would be a situation where the gas warms and basically creates an air bubble in the fuel line. That restricts the flow of gas through the line, something that is more problematic because the fuel pump is sucking the fuel from the tank, rather than pushing the fuel out of the tank. It's basically easier for a pump to push rather than pull. The most any pump can pull is about 33 vertical feet or so, where you could have a pump push liquid hundreds of feet.

So basically if you have a vapor lock condition three things will make it better: (1) Cooler temperatures; (2) A less restrictive fuel filter; and (3) A higher level of fuel in the gas tank.

[Goodspike]

I know the OP has already spent a lot of money, but what do people think about upgrading to a 4 barrel carb? I would think that would make it more efficient at slower speeds and increase the power some if the overall size was not increased too much (although more power applied to a 1976 drivetrain might not be a good idea).

[MinntoMich]

Originally Posted by Goodspike

I know the OP has already spent a lot of money, but what do people think about upgrading to a 4 barrel carb? I would think that would make it more efficient at slower speeds and increase the power some if the overall size was not increased too much (although more power applied to a 1976 drivetrain might not be a good idea).

Aftermarket TBI from JC Whitney or whoever. Add a new pump and O2 sensor. $800 to $1000 maybe but never a carb problem again. No pumping... No flooding... No choke problems... Maybe more power and better MPG.

I thought strongly about it on mine but upgraded to the 1990's instead. I added 10 feet, 6000 lbs. GVWR, went to a big block with TBI and overdrive and got better mileage and power.

[Goodspike]

Originally Posted by MinntoMich

Aftermarket TBI from JC Whitney or whoever. Add a new pump and O2 sensor. $800 to $1000 maybe but never a carb problem again. No pumping... No flooding... No choke problems... Maybe more power and better MPG.

I know those things exist, but I've never had experience with them to know how well they work. Carbs tend to be a PITA over the mid to long-term, but the FI systems I'm familiar with have all been designed for the specific application.

[Morich]

What point on the trip is going to be a factor if the OP has not been that route before.
A '76 RV running 70 and factor in you will be going uphill once you pass the middle of the country? I would expect the old rig to be breathing pretty hard!
Could be a problem or it could just be asking a lot.

[MinntoMich]

"I've now been keeping it above half tank and mostly avoiding the issue, but it still putters occasionally and slows me down to 40/50mph for a little while - even around 3/4 full tank."

So.... How fast does it recover from slowing you down at the side of the road or in a moving lane? Are we talking seconds or minutes?

How often is this occurring? Every hour, half hour, ten minutes?

Have you done any work or replaced anything recently that is related to the fuel system?

[Winterbagoal]

Originally Posted by Goodspike

I know the OP has already spent a lot of money, but what do people think about upgrading to a 4 barrel carb? I would think that would make it more efficient at slower speeds and increase the power some if the overall size was not increased too much (although more power applied to a 1976 drivetrain might not be a good idea).

Upgrading to a 4bbl carb would also include upgrading the intake manifold, as well? Could start to get pricey if it's a high end polished ported manifold like an Edelbrock, or similar.