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redynvre 09-15-2004 10:56 AM

Fuel pump
Hello Everybody,

I have a quick question: I installed last night the new mechanical fuel pump. Everything whent fine except that it was very hard to tight the pump all the way against the engine block. I am assuming that it is because it made the pump arm flex against the the rod, and therefore tension the spring?

I prefer to ask just incase I did something wrong. BTW the pump lever is correctly positionned against the rod.

I hope I am clear enough... My english vocabulary is showing its limits...

Thank you all!


swebster 09-15-2004 11:19 AM

Francois. Yes...if the cam lobe what pushing the rod out when you removed the old pump then you would need to overcome this tension when re-installing the new pump. Just be sure that the new pump is properly seated on a new clean gasket and that everything is seated correctly.

Make sure you watch this on first startup to be sure you have no leaks.

87MH 09-15-2004 11:21 AM


Originally Posted by redynvre
I have a quick question: I installed last night the new mechanical fuel pump........

Francois -

Is the electrical fuel pump working?

Even a brand new mechanical fuel pump will have a hard time "sucking" fuel from the tank THROUGH a non-working fuel pump.

From your earlier posts I understood your electric fuel pump was not functioning.

Even though some fuel will be drawn from the tank by the mechanical pump, a sufficient amount of fuel will not be delivered to the carburetor with out an operational electric fuel pump. The reason for this is the extremely long distance between the tank and the engine on the 345's (the tank is all the way to the rear), and the probability of some cracked hoses on these old(er) units. There are many documented instances (including mine) of the mechanical pump (on the 345's) not being able to "do it alone". They will deliver some gas, but could cause a "lean burn" condition in the cylinders due to insufficient gas, and COULD just stop for a while, then decide to go again.

Guess how I know.

Change the electric fuel pump (or determine why it is not working) if the existing electric pump does not deliver a good stream of gas to the mechanical fuel pump.

redynvre 09-15-2004 12:02 PM

Well, a couple of weeks ago, I checked under the rig to see where the electrical fuel pump is, BUT, I couldn't find any. Is that possible that there was none?

Or is it an intank pump? PLease tell me no! (My gas tank is full!)

I didn't see any wiring either.

Fruther info will be greatly appreciated, thanks!

I am planning to install an electrical fuel pump a little later.

And thanks Steven, that was excactly what you described. I sure will make a note of checking for leaks after running the engine a little.

Thank you for all your help!


swebster 09-15-2004 12:29 PM

On the 345 the electric fuel pump is mounted on a bracket right in front of the fuel tank. It sits within a transverse "C" channel between the frame rails. I don't know from your post if you have a 345 but this would be a good place to start looking.

Also - I had a number of fuel related issues and replaced both the electic and mechanical pumps. My issue turned out to be fuel filter related. There are three; one on the line from the tank into the electic pump. One mounted on the outside frame rail behind the battery locker and finally a paper element in the carburator itself. All three are available at AutoZone or NAPA.

swebster 09-15-2004 12:30 PM

Oh...just saw your tagline. So it should be in the same place on your 345.

For a quick check on the electric pump operation. Turn on the engine and let it warm up and kick down to low idle. While on a level surface, keep it in park put the parking brake on, get out and listen for a slight electricl "buzzing" sound near the tag axle. If you here this then the pump is "on".

Other things to consider would be that the pump is only on with the ingition and some 345's have a low oil pressure switch on the engine that would cut off the electric pump in the case of sudden oil pressure loss. This switch can fail and "shut off" the pump in error.

Dennis' point about crakced hoses is a good one. Most of the fuel line on the 345 is hard line. There is very little rubber hose in there. Now is as goos a time as any to replace all of it.

redynvre 09-15-2004 01:13 PM

Thank you Steven,

I have been reading all the other threads on th matter before, and I couldn't find my rear electric pump or the fuel filter before it. I did find however the one behind the battery compartment, in the chassis rail, which I also will replace tonight. Same goes witht he one in the carb.

I will look again for the rear pump between the tank and tag axle, I must have missed it. Do all 345 have a rear electric pump for the factory?



swebster 09-15-2004 01:41 PM

As far as I know the longer units had them installed for the reasons Dennis mentioned. Too far for a gravity feed to the mechanical pump. If there is no filter in the line from the tank to the pump then install one! Debris from you tank could easily kill your electric pump.

Typically this would happen on a summer day while climbing a huge moutain at least 50 miles from the nearest town - or maybe thats just me ;)

redynvre 09-15-2004 01:58 PM

Hehe, I hear you! That will be done!

I am thinking of installing clear body filters so it will be easier to monitor what's happening. I may wrap them with aluminum foil to protect the clear plastic from the elements.

I would add a nice thunderstorm to your senario! Hehehe

redynvre 09-16-2004 10:32 AM

Hello everyone!

The pump is in. I did also change the fuel filter behind the battery drawer. Now, I tried to crank the engine (not for long) and obviously it didn't start, probably because there may be too much air now in the lines.

Is there a need to bleed the lines first, or will the pump do it while you crank?


I looked again under the back of the rig, between the gas tank and tag axle for the electrical fuel pump. I didn't find it. :confused: Is it then between the tag and the grey/ water tank that is located between the gas tank an the tag on the passenger side?

I am really confused with that one!

Thank you for all your help!


swebster 09-16-2004 10:49 AM

The electrical pump will prime the lines. Should not take more than 90 seconds of cranking to pressurize up to the mechanical pump. Of course if this is still inoperable then the mechanical will not pull enough fuel from the tank to fire the engine.

The electric pump is located in the center of the coach directly in front of the gas tank and behyind the black water tank (in between the tag wheels). you will have to crawl under there to see it as you need to look up at it. The best thing to do is crawl under there (on a creeper if you can) get your head right under the forward edge of the fuel tank and look up. You should see the pump. A fuel line comes from the top roadside of the tank, enters the pump, then exists the curbside into a pressure regulator, then up the curbside framerail to the filter you just changed...ultimately into the mechanical pump.

Since you have an 85 I suppose it is possible that you don't have one! I heard from Dennis (87MH) that these pumps could have been added in later model years due to fuel delivery problems showing up on early model years. If this is the case let me know and I'll shoot some pics for you of the factory setup on my 86 so you can duplicate the configuration.

cooperhawk 09-16-2004 11:23 AM

On the electric pump you need to check if it will pump gas. On my pump, you could hear it running. When I placed a can under the hose from the outlet of the pump there was no gas being pumped. I replaced it and it solved all my problems of running out of gas when going up hills.

swebster 09-16-2004 11:24 AM Gunter has an 84 with an electric pump! Chances are good you have one in there Francois - keep looking.

redynvre 09-16-2004 02:55 PM

Hello Steven and Gunter,

I see exactly where you want me to look: This is the area were the safe well is, right?, all I see threre are the flexible fuel lines leaving the gas tank to go to the metal lines at the level of the grey/black water tank, right before the tag weel. All of this on the passenger side. I did look in the rails too.

I tried to go between the tag weel and the main rear axle: I couldn't really get to there, but I didn't see anything.

Then, in front of the main rear axle, all you see are the metal fuel lines coming from the rear to the fuel filter behind the battery drawer, and then move forward toward the mech. pump.

Now, Kragen Autoparts told me that for that chassis/year they have a part number for an intank fuel pump. I know that accuracy is not exactly their cup of tea.

But where could it be? How big would the pump be?

Thank you for your help!


swebster 09-16-2004 03:25 PM

If you followed the lines from the tank to the frame rail you would have see the fuel pump (about the size of a pepsi can with an inlet and outlet and two wires on it.)

Sounds like you do not have an electric pump.

garry 09-16-2004 03:46 PM

"If" you ever have to replace the mechanical pump again and it is hard to compress to start the bolts "bump" the engine over just a bit to move the cam lobe to relieve some of the pressure.


redynvre 09-16-2004 04:20 PM

Hello Garry,

Bump? Do you mean crank the engine once or twice?



cooperhawk 09-16-2004 04:24 PM

The electric fuel pump is located between the rear tag axle and the front of the fuel tank on the passenger side. There is a metal channel that goes between the driver and passenger side frame and is located between the front of the fuel tank and the rear of the main holding tank. The pump is fastened to this metal rail approximately 6 to 8" from the inside of the passenger side frame by the fuel lines. I purchased my pump from Autozone. The number on the box is E84070. It was an exact match to the pump I replaced including wiring, mounting brackets etc.. Make sure you install a fuel filter on the intake side of the pump. The fuel filter is also standard from the factory.

garry 09-16-2004 04:26 PM

Yes, you can use the key but don't crank, you just want to move the cam a few deg.
Makes all the difference in the world to get the lobe in the right position.

ALANSD 09-16-2004 04:27 PM

bump means to slightly turn the key to give voltage to the starter, but not enough to start the motor. You can pull the coil wire off it you think it might actually start up, to prevent that.

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