1. '88 YJ fuel pump issue

    I'm new to the Jeep Owners family and have what may amount to a stupid question but here it goes. I bought a '88 Jeep YJ 4.2 6 cyl that sits on 35's. It's been a fun jeep for the last 2 summers but I've had issues this summer. I replaced the carter carb a while back and went with the weber setup. It ran great unitl here recently. If it sat for a couple days it wouldn't start. A little fuel down the carb and it would run great again and be fine until it sat a few days again. In my past experience (mostly mopar) that would point to a failing fuel manuel fuel pump. I discovered this jeep has both a manuel and electric fuel pump. The manuel on the block and the electric on the frame back at the tank. The electric runs and is hooked up to the oil pressure switch. I bypassed the manuel pump but that didn't keep it running once you drove it for a while. But with the return line on the filter at the carb, which I've never seen, I thought maybe just a regular fuel filter would be the answer. I haven't tried that yet because I'm still not understanding the whole manuel and electric fuel pump thing. Is this normal?? Or is this something the previous owner did for whatever reason. I was just going to replace the manuel pump but if I can bypass it I'd rather do that. Any suggestions on how/why it should be set up?

  2. #2
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    Re: '88 YJ fuel pump issue

    that's interesting! All electric fuel pumps I have seen from the factory were all in the fuel tank and not the frame rail. I suspect someone put it there for some reason. You may want to call a dealer or get a manual to see if indeed it came with two pumps and sounds like one of them may have went out. The carb may just need a good adjusting too.

  3. #3
    That is quite the setup...... To the best of my knowledge, the 258 didn't come with an external electric fuel pump and certainly not with both electric and manual.

    It sounds like you have more than one issue. If you research the Weber, I'll find that the electric pump is the way to go. I would completely remove the mechanical pump, install a pump block-off plate and install a regulator w/pressure gauge aft the filter at the carb inlet. Ideally the Weber will perform best with the steady stream from the electric pump regulated down to 4-4.5 psi with a straight feed into the inlet. They don't work optimally with the pulsing pressure from the mech pumps and don't like the pressure created by them either. You can use your return line but you need a quality regulator that has its own return outlet built onto it (aka a pressure return valve or PRV). Holley makes a very good regulator for this bit they are costly.

    Once the plumbing is worked out, you will likely need a rebuild for the carb.

  4. #4
    Along with the good information already pointed out, you might want to run a different line on the electric fuel pump if in fact that it is spliced in with the oil pressure wire. The oil pressure line will have a variable resistance in the wire when hooked up to the pressure switch and will eventually shut down the fuel pump when the oil pressure switch gives that circuit enough resistance. The fuel pump circuit should always be at 12v or battery voltage when the ignition is in the on position. As for the " no start" after sitting for a day or two, the carb should have enough fuel in the bowl to get the engine going after a couple of pumps from the pedal. If that bowl is depleted of fuel, this would indicate that the fuel is siphoning back to the tank after sitting for a while. An inline fuel filter will help you keep that from occurring granted that there's no leak in the lines.
    Confucious says: Don't eat the snow where the huskies go!

  5. #5
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    Re: '88 YJ fuel pump issue

    I understand and agree with the postings pertaining to this carburetored jeep with electric fuel pump in regards to loss of fuel in float bowl drain back possibly due to pump check valve or pressure loss but my question is and was mentioned as well , is it possible that this weber carburetor may leak fuel from its float bowl through fuel well plugs ? GM dual jet and quadrajet were famous for that and had to have their plugs reseated and epoxied to prevent this problem and to eliminate rich mixture and rough idle and stalls as well . Had my hands on a few 2 and 4 barrel electronic and non-electronic and each one leaked to some degree. Just wondering does this happen to the weber as well ? The original carter YF carb was less than trustworthy as I rebuilt my brothers YF on an '84 XJ and although it worked , a better carb could be chosen.
    It just barely passed emissions , even the tech couldn't tune it better than my brother and I .
    He said , " get a Holley or what you can find for it , but get rid of that carb ! " . And that was over 15 years ago . Can't be any better now. Hope the weber fares better !

  6. #6

    Re: '88 YJ fuel pump issue

    Hey Greg…… Long time Bro! I like your thinking… But consider this:
    Theoretically, no the Weber would not drain into the ventrui from the bowl….. But anything is possible???? All Weber down draft carbs have an emulsion tube (E-tube) on each circuit that is at open atmosphere. In terms of fluid movement/dynamics, it’s an effective air gap. With that said, if they were clogged, plugged (poor fuel quality, debris, etc.)or otherwise not open to the atmosphere (maybe a really dirty air filter….that would be a stretch though) it could happen. Or if the body had a crack internally, but he would likely have poor idling and flooding. But like SteelHeadz said, it could easily siphon backwards from the bowl.

  7. I removed my carter carb about five years back from my 87 4.2. I have used the manual fuel pump on the engine ever since. I have not ever had an issue with it and wheel very hard on a regular basis. Starts good year round and runs and idles great. The carter used to puke brown smoke out tail pipe at any angle that wasn't compl flat!! One of the better investments I have made to my rig!! I would start with a fuel pressure gage and go from there before I started to buy more parts that will not fix you're problem. As long as the fuel lines are all in good shape then I would have to say you are having a fuel delivery issue... Get rid of one of the pumps and just go with one that you know is operating correctly. And make sure it is plumbed correctly as well. Good luck!! The webber carb is a very wise choice... The same one is used on many VW air cooled engines as well. (Oh another quick thought--- when I ordered mine from quadretac there was several jet options. I would make sure that you are running a 32/32 or similar. There is also an option for 32/34 or 34/36 jets which would cause issues on a stock engine)

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    Re: '88 YJ fuel pump issue

    Quote Originally Posted by PoliceMonkey161 View Post
    Hey Greg…… Long time Bro! I like your thinking… But consider this:
    Theoretically, no the Weber would not drain into the ventrui from the bowl….. But anything is possible???? All Weber down draft carbs have an emulsion tube (E-tube) on each circuit that is at open atmosphere. In terms of fluid movement/dynamics, it’s an effective air gap. With that said, if they were clogged, plugged (poor fuel quality, debris, etc.)or otherwise not open to the atmosphere (maybe a really dirty air filter….that would be a stretch though) it could happen. Or if the body had a crack internally, but he would likely have poor idling and flooding. But like SteelHeadz said, it could easily siphon backwards from the bowl.
    Thank you sir ! Well , it seems the. Weber is designed to be superior for jeep duty and I think that carb should be made to work with whatever it takes , you long time CJ owners/mechanic/restorers should know ! But drain back sounds like the problem . An electric fuel pump should be made to work , I would think , but the mechanical pump w/pressure regulator , adjusted accordingly has always been tried and true for you guys ? I believe.
    years ago , we used them on two cars , a GTO w/Holley double pumper and a small block 350 AMC rambler ( clone SST, a little short on 343's) to prevent fuel starvation accelerating/decelerating. But yeah, consistent pressure is priority running and starting.
    Man, am I glad a weber does not drip into the intake like a Rochester , what a drag!
    I sure appreciate the lessons from you experienced jeep owners as I am too stuck on my electronics FI XJ and haven't had my hands on a carb since my '85 olds and '83 Grand Prix .
    Still know carbs , but ya get rusty if you don't turn a few idle mixture screws once in a while .
    i know 69jeepcj knows what I mean too as he must always be tuning his hot rod CJ for making trenches off road as well as perfecting his 60 foot times down the trail ! Yee HA !
    I know your working hard on your 304 CJ , once done , all CJ owners fixing up their jeeps will get some good tips from ya to dress for success ! Every time I see pics of your ride , I get hot to dream ways to find the money to jump on one , but got to wait my turn , unfortunately got priorities that take precedence . As I vowed , somehow I will . But I thank all you guys for these priceless lessons on CJ iron ! Thanks to all . Greg

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    Re: '88 YJ fuel pump issue

    Quote Originally Posted by richgilbert81 View Post
    I removed my carter carb about five years back from my 87 4.2. I have used the manual fuel pump on the engine ever since. I have not ever had an issue with it and wheel very hard on a regular basis. Starts good year round and runs and idles great. The carter used to puke brown smoke out tail pipe at any angle that wasn't compl flat!! One of the better investments I have made to my rig!! I would start with a fuel pressure gage and go from there before I started to buy more parts that will not fix you're problem. As long as the fuel lines are all in good shape then I would have to say you are having a fuel delivery issue... Get rid of one of the pumps and just go with one that you know is operating correctly. And make sure it is plumbed correctly as well. Good luck!! The webber carb is a very wise choice... The same one is used on many VW air cooled engines as well. (Oh another quick thought--- when I ordered mine from quadretac there was several jet options. I would make sure that you are running a 32/32 or similar. There is also an option for 32/34 or 34/36 jets which would cause issues on a stock engine)
    that is a point very well made , do not over enrich the fuel delivery as you will flood the venturis for sure with too large main jets with stock engine vacuum pulling idle, off idle, and cruise. That's only good on high idle non-stock radical cam engines which off road jeeps do not proper from. Lean enough jets and the mixture screws will take it from there for stock six cyl. and 304's , even a 360. You can't expect more fuel to make more power of the engine parameters can't keep up. Stock air flow needs stock fuel feed , hence , stock jets. At most , if you open up the cylinder head volume by porting for better flow and a better intake , only then will you try bigger jets if cam is stock or close and vacuum too. These are jeeps for low rpm , low speed and low torque , not quarter mile.
    But sometimes I think I'll need two jeeps , one stock and one for a 350/350 small block !
    Nothing like spitting out dirt as you get threw the gears ! But the YF is just a cork. I think it was to detune the engines back then for "fuel economy" and production cost cuts. Thank you weber for stepping up with a proper carb as weber's always were , dirt and street. Thanks. Greg

  10. #10
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    Re: '88 YJ fuel pump issue

    Quote Originally Posted by 69jeepcj View Post
    that's interesting! All electric fuel pumps I have seen from the factory were all in the fuel tank and not the frame rail. I suspect someone put it there for some reason. You may want to call a dealer or get a manual to see if indeed it came with two pumps and sounds like one of them may have went out. The carb may just need a good adjusting too.
    I agree , I have never heard or seen an electric fuel pump used in line with a mechanical fuel pump on anything. It one or the other. You cannot push that much pressure to a pump that produces 5-7 psi average with three or four time the pressure. Why would someone do that ?
    I understand that an electric pump with a regulator will give consistent pressure but this fuel system is plumed out wrong , I think. Makes no sense for stock or anything else.
    No question though , fuel pressure must be checked and lines inspected too but yeah , factory electric fuel pumps normally are in-tank for efficiency (cooling) and better pick up .
    Yeah , once pressure is established , mixture setting can be done more effectively as there is no way you can get the engine to idle clean without consistent pressure and volume. I hear that.
    don't know YJ's real well but I remember one I6 carbed and I really don't think it had an electric pump in line with mechanical . They only got one tank so it would not be for auxiliary either . Don't sound right. Either electric to a pressure regulator of some sort or a mechanical pump , cannot have both. A friend had a '84 Buick 231 v6 electronic two barrel carb with electric fuel pump but NO mechanical pump. Must have been real low pressure not to float the needle off the seat ! Just too wired , but wrong I think ( the electric/mechanical set up). But definately interesting ! Thanks . Greg

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