On the way between Albuquerque and Santa Fe, our engine suddenly started to lose power. A few times, we were able to recover after about 10 seconds, but gradually things got worse and worse and eventually we found ourselves stranded at the side of the road, just outside Santa Fe, on a Friday afternoon. Not great. We called several truck service centers, but no one was able to help until early or mid of the next week! Luckily, one of them recommended we call a mobile mechanic, Gerardo Bencomo at Redline Repairs, and he saved us!
The problem
Typically, when an engine loses power, the most common reasons are issues with the carburator or with the supply of fuel. Gerardo was very systematic on how he approached the problem. He led the engine cool down for about an hour and then tried to start it. He disconnected the top of the carburator and removed the air filter to look inside and see what happened. The quadrajet carburator showed no obvious problems. We saw fuel come out of the jets. Then, with the engine turned off, he inspected the fuel line, starting from the tank in the back and making his way forward, checking the fuel filters to make sure there was no obvious obstruction. Everything looked good, until we got to the mechanical fuel pump. Here’s what we saw:
The transition hose going into the mechanical pump had to make a 180 degree turn and was pinched in the middle, making it harder for the fuel to get through. While the truck service centers we talked to immediately jumped to the conclusion that our mechanic fuel pump was broken, Gerardo identified the issue correctly.
The solution
Replacing the transition hose
We had to replace this part. Gerardo decided to make a custom copper part that would prevent pinching from happening ever again. You can see he knows what he’s doing by correctly flaring the ends of the copper tube he is using to replace the rubber hose.
Vapor Lock
Another potential reason why the engine might be stalling is vapor lock, which is a known issue for 80s Airstream motorhomes. Vapor lock is the effect of fuel boiling and turning into vapor before reaching the mechanical fuel pump. Because the fuel pump is designed to pump a liquid, not a vapor, it results in the engine being starved of fuel and stalling.
Vapor lock can happen when it’s really hot outside (check!) and/or when on high altitude (check!) and/or when the gasoline contains ethanol (check!). Airstreams are especially susceptible because 1/ the fuel lines are really long since the gas tank is mounted in the back; and 2/ the mechanical fuel pump pulls fuel by creating underpressure, hence lowering the boiling point of the fuel. Vapor lock is potentially very dangerous because when the engine stalls the brakes and power steering stop working. If this happens on a descend, this could potentially be catastrophic.
We don’t know if vapor lock might have been a contributing factor, but just to be on the safe side, and because we are crossing the mountainous West, we decided to install an auxiliary electric fuel pump, close the fuel tank. This will prevent vapor lock because it will actively push fuel towards the mechanical fuel pump, reducing the likelihood of underpressure causing the fuel to turn into vapor.
We installed an Edelbrock 17301. It has the right pressure range (4-7 psi), so no pressure regulator needed. Because it is self priming and will allow fuel to pass through even when not powered, we don’t need a bypass line. To be safe, we installed a lighted switch upfront to be able to manually turn the pump on or off. This is an important safety precaution in case the motorhome gets into an accident. You don’t want fuel to keep pushing forward when things go bad.
We also started paying attention to ethanol. In most gas stations, up to 10% of the gasoline content could be ethanol, lowering the boiling point. We found this great web site that lists the gas stations that don’t add ethanol. From that point onwards, we always went with ethanol-free gas.
But there’s more …
Gerardo also discovered that the passenger side dualies wheel seal was leaking and the back airbags were shot. The airbags are a whole different story. As for the wheel seals, look at the image below. It shows the bottom of the brake caliper wet but the top dry. This is indication of wheel seal leaking (as opposed to the brakes leaking).
So, while we’re at it, why not also replace the wheel seals. And that’s what we did:
We broke down on Friday afternoon. By Sunday morning we were back on the road with a new fuel transition hose, new electric fuel pump, and new wheel seal. We’ve since driven over 1,000 miles with no issues. Thank you Gerardo!
Next Steps
Once back home, we are going to replace the wheel seal on the driver side as well. It wasn’t leaking, but better have the seals on both sides be in the same condition.
Also, we’re going to change the Edelbrock power source to be in line with GM’s recommendations. Rather than just being wired to the ignition, it needs to be hooked up to the oil pressure switch. We’re also considering adding the bypass line and check valve as an extra security.
