Dear RV Doctor,
In an earlier issue of RV View you answered a question about vapor lock with the suggestion of adding a second electronic fuel pump among other remedies. Recently I bought an older (1993) Ford 350 Frontier Flyer. The main difference is that it is fuel-injected but I believe it, too, is vapor locking. Some people I have spoken to were surprised it is fuel-injected and said that they had never heard of a fuel-injected motorhome vapor locking. Can vapor lock occur in a fuel-injected engine and if so, do the remedies you suggested in the earlier article apply? If not any ideas on what it may be? It is definitely a temperature related issue because after it cools down it will run fine.
–Dallas Drewry, (Salt Lake City, UT)
Yes Dallas, vapor lock can occur when using an in-tank high pressure pump to deliver fuel to the engine. It is my belief there are at least three possibilities that may cause the problem you are experiencing. First, Ford had a recall on in-tank fuel pumps and pressure regulators for 1990-93 model year vehicles. It is possible that your in-tank fuel pump or pressure regulator may be a faulty component. Others agree with me that you should focus on the pressure regulator first, because if it fails it would not allow fuel to return properly to the fuel tank. This could cause the vapor lock problem because it would literally boil any stagnate or stationary fuel before it gets to the injector. Have an engine mechanic confirm that the pressure regulator is within factory specifications.
Second, as mentioned above, the in-tank fuel pump itself may be the problem. That in-tank pump is of a type that is highly susceptible to damage from contamination. As the pump begins to wear, its output becomes weaker. If the pump is weak, the vehicle will lose power after the pump has warmed up. Again, have a technician confirm that the output pressure of the pump is within factory specs, especially after the engine has warmed up.
And thirdly, the final possibility is that the fuel lines may be heated beyond design parameters. This typically happens when the fuel lines and exhaust manifold follow each other too closely along the frame rail. This could be the result of a faulty catalytic converter or it could be the result of ill-placed or missing heat shields in that area. For more specific information regarding the specs for your chassis, I recommend you contact Transfer Flow Inc., in my opinion the premier authority on all things relating to RV fuel containers. Feel free to contact Bill Gaines at: [email protected] or give them a call at 800-442-0056.
(Please feel free to comment, however, please also note that due to the volume of communications I receive from multiple channels I cannot guarantee a personal response in every instance. However, questions of an overall general interest may be considered and published in an upcoming RV Doctor column.)
Need your Help. I have a 1995, 36 ft Coachman motorhome with the 460. I have had to have the fuel pump replaced for the 3rd time in 3 months. I understand that it may help to put and electric pump on the frame in front of the fuel filter. Ford dealers have replaced each filter for me, is there something they are orver looking? Help me please this is costing me alot of money each time.
I own a 85 southwind, 24 ft 454 chevy. On hot days I experience Vapor Lock, Will adding a electric fuel pump near the tank with a switch on the dash correct the problem? do I need to recirculate the fuel back to the tank? any advice will be appreciated, and vacations will become relaxing once again.
Be careful about which replacement fuel filter you put back on… some are not as good as the OEM ones… they actually say they filter better… which is true…. but then offer more restriction to the fuel flow through them… so best to check and ask questions… and even then do the experiment…
Yes we found that a bad fuel filter (dirty) does take the pump out and cause these kinds of problems… a lot of the times…
That being said… with the addition of the E85 gas… we are going to see a lot more fuel problems shortly as it gets added to the gas these days… The blend of lighter items will support more cavatation (vapor locking) of the fuel pump when it gets hotter… as well as your gas mileage is going to go down with the advent of the additive.
We change our filters now yearly… and while under their look at all the hoses for cracking and problems also… and havn’t had any problems since…
HAVE HAD WHAT I CALLED A VAPOR LOCK TWICE ON MY 1994 FOR 460 MOTOR HOME…MY SON, MR. GOODWRENCH MECH. SAYS FUEL INJECTED MOTOR CAN NOT VAPOR LOCK AND IS FUEL PUMP GETTING WEAK OR GOING OUT…IN BETWEEN INCIDENTS WAS ONE YEAR AND HAS BEEN 7 MONTHS SINCE LAST…BOTH HAPPENED ON HOT DAYS IN AZ AND NM…ONE TIME WAS PULLING INTO WAL MART AND STAYED OVER NITE AND OTHER TIME SAT FOR AN HOUR OR SO AND THEN MADE TO ROADSIDE PARK …WILL SAVE THIS ARTICLE AND SHOW HIM WHEN I GET TO SEE HIM IN APRIL…HAD A NEW FUEL FILTER ON AT THE TIME BY THE WAY…
ha gary back in 93 ford had a lot of recalles on there sys you need to check fuel filter frist as ford had two inline filters one was under the master cly on fram and the other was a small flat cannester along the frame they also had prob with fuel psi switch you need to get someone to check psi on fuel rail should be like 5060 psi if you have the old comp under the hood they also had heat prob with that when it gets hot it shuts down then when it cools off it starts up like nothing happen they also had prob with the modul down by dist [ ele points] when it get hot it whould shut down cool it starts backup like nothing happen you didnt say what engin you had but it probble was a 302 fuel inj Ihad 1996 with same prob tryed everything then found it to be under hood computer theres a ford web I thank it was ford.com you can see all recalls on any year
Well.. I think you forgot one main improtant thing in the system.. the fuel filter… seems that when they start to get dirty.. they restrict the free flow of fuel.. the pump.. pumps harder.. and starts to cavitate in the fuel tank… thus you get vapor instead of all liquid..
This then masks the real problem by presenting itself with the same as vapor locking.. it really is…
Before going to get the pump out of the tank… I would try a new OEM fuel fiter in the line… and not to say others are not good.. but we found the OEM ones work the best and longest…
Check the owners manual for the vehicle.. I think you will find it says to replace it… every so often by mileage… but we have found that you also want to change it out every year or so… they don’t last forever .. and yes they do get dirty enough from even the good gas to start to plug up.. and restrict the fuel.
One other thing that we have also found is that the fuel pump when it has to work harder… doesn’t last as long either.. and need s to be replaced more often…
Fuel injection is a good system .. when kept clean…
We bought a used Forest River Lexington B Plus last Spring that we are enjoying except for: on interstate highways at higher speeds it is not comfortable to drive. We are thinking of replacing the shocks with Bilsteins and or heavy duty sway bars. Any suggestions?