electric fuel pump

[85holiram]

Hi all, the amount of info on this site is absolutely invaluable, thank you all so much! (first post, though I have been signed up for awhile) On to the problem.....85 Holiday Rambler, 454, TH400, the usual. Generally whats been happening is starts OK but never engages high idle. Warms up slow. will start out and be OK on level ground, start up a hill and it missses and bogs down to the point you just can't go anymore. Had it towed home from center lane of Freeway in rush our city traffic. Been fighting this for awhile. Changed all filters,did plugs, cap and rotor recently, ran better but still bogs on hills, only went about 4 miles round trip with 1 short hill. I have replaced all vacuum lines with exception of vacuum booster to for tag axle, will do that soon. a little more background, carb was rebuilt about 3 years ago by a mail in rebuilder. I rebuilt carb last year, still ran poorly. probably 10 years ago (and maybe 2000 miles) there was a leak at the fuel pressure regulator,so I removed it to get home, ran flawless the 900 miles home that time. By the way the regulator was between tank and electric fuel pump, not after fuel pump Sorry this is long winded, but I figure more info the better. My plans: new regulator, test pump for flow and test mechanical pump for flow. Any suggestions would be appreciated!

[tmsnyder]

Can you measure the fuel pressure at the carb?

[Rickf1985]

Like TM says you need to get the pressure at the carb. The regulator HAS to be after the pump, does nothing before it. The original pump would have been in the tank but 85 is around the time they were changing over so may or may not have a pump in the tank. Is the pump running while the engine is running? Did you change the filter that is hidden in the line between the rear and the front? It is usually in the vicinity of the side entrance, an inline filter. This filter is missed a lot and after 33 years it may just be clogged.

[85holiram]

I will have to make up an adapter for fuel pressure gauge.I did change the filter on the side rail (between the heat shield and the propane tank...Sheeesh!) I have not determined if I have an electric pump in tank or not. I have turned on the ignition and jumped out and looked under and heard the pump running. It didn't dawn on me  to check while engine was running. When I first discovered the regulator leaking while 900 miles from home I didn't even realize what it was,  once I looked at it closely and realized what it  was I thought it was weird where it was placed. I do have original receipts showing a holley pump and regulator so I'm guessing whoever put it in didn't understand the function. BTW, thanks for response. I have to get exhaust hooked back up before I test pressure, probably next weekend. I also thought I would go ahead and get a new regulator and place after the electric pump.

[Rickf1985]

I am curious, when the regulator was leaking was it leaking with a bit of force? If it is on the suction side of an electric pump it would not tend to leak since it would have a little vacuum to it. I am wondering if you have an electric pump in the tank and it is running in addition to the one on the rail! That is the only way I can see that the regulator would leak. It would have to have pressure on it from the tank side. I would disconnect the line from the pump and put the line from the tank into a can and have someone turn the key on, see if you get and gas out. If you do then bypass the pump on the rail and disconnect the wire but leave it there in case you ever need it.

[85holiram]

thanks rick,I will check that. if that turns out to be the case then the only thing I can see for the leak is maybe cracked case, really bad diaphram, or gasket. the leak was a drip noticed by my brother-in-law before I started the MH to head home.we removed it and just ran the line to the pump.I will try to test that tomorrow if I have time. I'm retired which means "Dad could you fix this for me", I'm in the middle of "helping" putting a rebuilt motor in my sons Cherokee)  W% I'm waiting on other parts for the MH so I can't start it right now but can check the the pump the way you said. I'll get back  to you with what I find.

[tmsnyder]

It should be low pressure, something like this would do it:


https://www.harborfreight.com/fuel-pump-and-vacuum-tester-62637.html

[Rickf1985]

I would go with the fuel pressure test kit that HF sells instead of the vacuum tester. Most electric in tank pumps will put out about 15 lbs. pressure hence the regulator. You need the higher pressure so you can get the volume you need.

[tmsnyder]

I was just giving the cheapest option for reading pressure at the carb.  Think it's $13. Yes it's a vacuum gauge (which is handy to have anyway) but it also reads up to 10psi.  For checking the pressure at the carburetor, should be 6-8psi I think.

The HF fuel injector gauge set goes to 100 psi, 6-8 psi would show up on the gauge but depending on the calibration of the gauge I wouldn't have much faith in the reading.  It would tell you yes or no there is or isn't pressure, but the actual value might be +/- 1 or 2 psi.

[85holiram]

Well I've not made much progress I did get under and check out a few things. I had always thought it was weird that their was not a filter before the electric add-on fuel pump. I was inspecting fuel lines and lo and behold tucked away ON TOP of the fuel tank was a filter. I pulled that filter and cut it open with a tubing cutter ( almost hoping it would be completely clogged thus solving my problem) It really did not seem to be all that bad, had some sand like grit in the folds of the media,but could still see through it held up to light. I have determined it does not have the in tank pump. The lines going to the top of the tank are pretty crusty and mushy so I think I will end up dropping the tank, cleaning and replacing all the lines.  the next thing I'm going to do is get the exhaust manifolds machined flat and reinstalled. I'm slow but I do get it done. So my post may not be all days in a row, but I do read all responses and  appreciate them. I do have a pressure gauge to use. I'm going to do the manifolds, then replace the filter and test pressure and maybe a test drive before I tear into tank and all hoses. Sooo, until next time wish me luck !

[85holiram]

Oh,forgot to say I am putting on a new fuel pressure pressure regulator, and check the volume and the pressure.

[Rickf1985]

Be sure you put the regulator AFTER the pump. The fact that there was one before the pump still makes me think there is a pump in the tank. If the lines are mushy they could be collapsing from the suction of the pump.

[85holiram]

Lines are definitely mushy. I checked VIN and chassis tags,says it is an 84. there is pretty fair clearance on top of gas tank, only electrical I see is fuel level sender wire. I'm going to drop the tank and redo all the lines etc. as outlined in motorhome chassis service manual, but for now I have delved into flattening exhaust manifolds. I just started another post on that. Thanks for advise Rick 

[Rickf1985]

84 may well have not had a pump in the tank. It was right around there that they changed things and started putting them in. Exhaust manifolds are a constant nightmare. Especially if you have the early cast iron ones. Most people just go with headers and if you plan to keep the coach for five or more years you will be money ahead to get a good set of headers and be done with the constant breaking manifolds. Do you still have all the emissions equipment? If you are still running the A.I.R. system that has a lot to do with the cracking manifolds since it burns excess gas in the manifolds.

[85holiram]

Decide to go for a test drive after putting in a new filter back by the tank as I talked about in previous post, I was rather shocked it drove flawlessly up and down steep hills. I babied it, I hit it full throttle, no hesitation ran like a man chased by a bear! I'm still going to do all the things I talked about as a point of restoration, but at least I can drive it (I think) with a bit more confidence. Thanks all