A delay in fuel pump may be due to either a "lazy" relay or an insufficient ground (fender, firewall, or pump itself) It could also be a poor connection at ignition switch. However I took a look at the wiring diagram I have and it seems that there are several items connected to the power supply for the pump, which I see no real reason for even being on that circut at all. Have you tried a code check?
Only thing other that I can think of would be the anti-drainback valve in the pump, but the pump should come on and re pressurize the system, not fail to run, even if the valve was bad. To find your problem, you are going to have to do a bunch of testing, till you get an idea what is happening. Just don't assume anything is good till it can be proven to be good.
I know I have not "cured your problem, but I hope I've given you enough to go on to begin testing.
Comments:
May 10, 2009
- I believe that the fuel pump has a resistor in the line somewhere...this may be the reason for the voltage change. I am wondering what condition the contact points in the relay look like. If they aren't clean, it is possible that they could be causing a voltage drop till they burn themselves clean. (I'm reaching a bit here but a wierd problem usually has a wierd solution) Also, have you checked the pressure regulator to see what it's doing? (also be interesting to see what actual fuel pressures are at any point in all this) I'm going to check on a few things and get back to you.
May 10, 2009
- OK...don't know if you tried this already, but it appears that the starter relay and the fuel pump relay are identical. Try switching them just to see if anything changes.
May 11, 2009
- looked at diagram to see if there is a resistor bypass to "kick" the pump when starting. that's why pressures through cycle are important. Only diagram I have for jeep is haynes it's worthless...shows three different systems and does not differentiate between two of them (to save paper?) One part shows system going through resistor relays, one shows pump running off of starter relay and other one looks like it goes through the ecm??? Glad It's not mine or hammers and window glass may meet soon!!!
Anyhow, pressures may tell you a bit more about what's going on.
May 11, 2009
- Following along with yth vacuum idea, try removing the fill cap. It may set a code if you run it that way but you will know what the code is and not be upset.
I actually use my old a/c gauge set to read rail pressure it fits on there fine and pressure is pressure!
Also, have you tried running an external ground wire there from the battery? That would eliminate any possibility of bad connection along the way. (If it was my vehicle, I likely would have run a new hot wire, resistor and ground with a toggle on the dash and a mercury switch somewhere to shut it down in a rollover. But, I'm a bit crazy, so don't do that!)
Haynes is likely the worst manual I have ever used...I once had an assortment of the big chilton, motors and mitchell manuals...All stolen along with a personal "source book" I had compiled over the years. Aside from not having a torch and welder, I probably miss those books more than anything!
May 11, 2009
- Messages got crossed in the "mail"...system is supposed to remain pressurized. That's why pressure test is important. I am also wondering if you may just have a defective pump. My general rule is that a new pump (or any other part) is good when it is working...not because I just took it out of the box. Quality control is abysmal (saw that coming when chevy stopped numbering connecting rods because the guys assembling the engines couldn't read the #'s !!! And, it's gone downhill from there.
May 12, 2009
- This is starting to look like a novel!!! Somehow I sort of assumed you did all that already. Don't hook pump up to battery and run it "dry" even if it's good it won't be anymore. Also I don't remember you mentioning about other pumps...could be that if there is a resistor before the pump, it has changed value and is burning up motor.??? I'll re-read everything later but don't remember you saying pump was new? (dosen't matter now anyway)
May 12, 2009
- A/c (air conditioning gauges) Self-diagnostics supposedly began in 91. ou turn the key on and off three times, leave it on third time and check engine light will flash #s in pairs: two flashes =#2 so two then one flash is twenty one then a pause and next #.Don't think fuel pump is in code library anyhow. (more geared towards sensors) If you drop the tank, look in there and make sure it's clean. Again I'd have to read this over but you did change filter???
Once they took the nickel out of the block and heads, then made the heads lighter, they were getting unreliable. Ran a few 283's (low 12 seconds and a couple of 10 second 350's in a '57. Really miss that car!
May 12, 2009
- First problem...you are reading the diagram correctly ((It's made for idiots) The "capacitors" are color changes and splices in the wire. I believe that the diagram is either showing two optional systems, What would make sense would be a full power bypass to the pump on startup then routed through the resistor. The splices bother me though...every one is a potential voltage drop or place where corrosion can breakdown the connection. From what I see, they serve no purpose. As far as ground goes I may have mentioned that on mine, because of all the problems I've seen stemming from poor factory grounding, I have two 10 gauge block to battery grounds and have "bonded" entire system (all fenders chassis firewall and dash ) with one continious single ground wire.And "00" welding cable from battery to starter. A ground is a ground which is why I mentioned connecting a direcrt ground wire from battery to pump wire.That way there is no loss of integrity.This is one of those cars that after everyone went home, I'd go back after dinner, lock all the doors crank up some cream or hendrix and go at it (after my guys tore their hair out all day) I'd go home when it was fixed, and, no extra labor was ever on a bill to customer.
Doing this here is more difficult...i can't see hear or touch anything and have to visualize what you have and hope I get good info back.
What i see now is a history of pumps failing so the one that's there is suspect. Power is also an issue, but you haven't run out of places to check (yet) All those "capacitors" are suspect voltage drop sources.
May 12, 2009
- Safe to jump pump but if it uses a resistor, you can't run it long or it will burn out. And you still won't get pressure info that's important. It can run, but if its putting out twenty instead of fifty you won't know it.(same about anti-drainback.)
May 12, 2009
- I'm gone for tonight...got to wake up at 4am and go shoot a turkey.
(the late worm dosen't get eaten by the early bird?)
May 12, 2009
- With all the attention on the fuel pump, I re-read your original post and noticed something...you mentioned that you need to run with your foot on the throttle after starting and that idle is too high...Have you checked the idle control valve (next to the throttle position sensor ) to make sure its clean and functional? If it's hanging up, it will mess with air volume on startup (change mixture). which you are then compensating for with your foot. If you remove it, don't loose the "o" ring seal and don't turn the valve end when cleaning. check the passageway to it as well & make sure that's clean too.Do same for throttle plate to make sure it seals when closed. Just a possibility, but we may be working on the wrong end of the car.
May 12, 2009
- I just reviewed all the stuff you posted under Alero...It seems that we all are going in the same direction. Two things that come to mind though are what I just posted about the idle valve and that you really need to know what kind of pressure and if drainback valve on the pump you have are good. Otherwise we will all be chasing our tails forever and when finished, will have written a new novel (Gone With the Fuel Pump?)
May 14, 2009
- This is the first time I've ever had to use the "scroll" feature on an answer!! I don't know what the resistance is supposed to be. Don't run pump on straight 12v long...it could burn out. The way I decipher the great diagram I have, I believe that the resistor is supposed to be bypassed through a relay for the starter motor, then, in "run" power goes through the resistor.(that would make sense) I've actually used a similar layout when building ignition systems. It doesn't need to cut down voltage by much, just take the "edge" off it. Like a Chrysler ballast resistor for ignition. I'm wondering if everything on the run side on yours is OK and the bypass wire from the starter relay isn't. That leaves one remaining question...what is causing the pumps to fail early?
May 14, 2009
- For a really long time now I've wanted to write a manual containing real stuff...especially locations of items, and everything you need to know about them. Unless you work in a dealership (one kind of car all day long) you never get to or have time to find out all that stuff. I've had cars that had things under the hood that I had no clue what they were..they never failed, and never had time to find out what they were.
And, I was in the business and was fairly competent (even had ase certs!) In my shop, we worked on everything, unless I didn't like the car...Then I wouldn't let it in the parking lot! (especially VW beetles and carman gias) Otherwise, worked on armored trucks to top fuel.
May 14, 2009
- Only an expert on Jeep fuel system....Aftert his, I think when my pump goes, I'm getting an external pump and regulator with an anti-drainback valve and wiring it my way...I'd really like to meet the people who design this stuff!!!
May 15, 2009
- You have an egr valve on yours? Haven't seen one on many 4.0 engines. I know they did use them. egr usually has more to do with how it runs after it starts...especially if it's blocked. Are you sure you have one? After all, you have to be making eg (exhaust gas) to r (recirculate) it. If the valve was wide open and unblocked it could have some effect, but don't go that way...it makes no sense.
May 16, 2009
- You just lost me...I don't have a good diagram (we know that) and I use my jeep for a reference vehicle a lot. Since I haven't had your exact problem I never had to locate the ballast resistor, (only resistor I see on mine is on the driver fender and I don't exactly know what that one is for, except that it's good) and do not have an egr on mine. Where are you finding this stuff?
When tracing wires on computer stuff, one thing I use that I did not mention. I attach a semi-used 1.5v (one that reads 1.4 or 1.3v) battery to the wire I can see, and disconnect the vehicle battery...then the only hot wire is the one I'm working on. and the voltage will not damage anything.I'm starting to think that the pump is just not right. Without pressure tests we won't know that.
May 16, 2009
- Believe it or not the pumps rrom the dealer are supposed to be better than any on the aftermarket. personally, I am likely to do what I said before and if mine goes bad I'll probably put an MSD unit in there with a back flow valve added. (external). You can probably use any pressure gauge that reads over eighty pounds. The rail fitting is exactly the same as on an ac unit.(why I use my old ac gauge on there)
May 19, 2009
- Crank and cam sensors are part of the ignition system and to the best of my knowledge, do not control fuel pump operation in any way
If cps was even partially failed, generally the symptom of the onset of failure would be unexplained stalling, then being able to re-start after a short cool down, followed shortly thereafter by a stall and no start (forever) condition. I'm pretty much convinced that either the system is not sending enough power on start up (to the pump) or that the pump itself is lazy, and not getting up to speed right away.
When dealing with electrical components it amazes me how they can develop new and exciting ways of failing. But, with proper testing (fuel gauge on the rail and meter on the pump connection) you can run aq good test to determine what is doing what, and when. Just saw some fuel gauges in a Summit race catalog that were not too expensive. you would need one hose from an a/c gauge set or as I said, anything with matching thread size.
May 22, 2009
- Well? Is it fixed or have you beaten it to death with a sledge hammer??? (I still mentally work out problems with cars that are long ago in the scrapyard...thankfully there were only a few of them)
May 23, 2009
- I will feel guilty if I get you to spend $200 on a new pump if it doesn't work, but I think after what is known so far, you could do that. Only question is the "why" only because I don't consider it fixed unless the cause is known and measures are taken to prevent a repeat failure. (I'd even consider putting a capacitor or resistor on the power side of the pump, to prevent "spikes") 11.5 is fine and I'll bet you get the same reading @ the battery when cranking.. Check the insides of the tank for any junk as well. You can also add an additional ground near the tank and tie the original harness wire to it. Unless the ground is open at some point during key turning. Unless there is something huge we both missed ,(I seriously doubt it) I don't see why it would not work.
Don't know what you do for a living, but sometimes you need to take a "leap of faith".
May 23, 2009
- Actually I'd rather see a ton of junk in the tank! at least it would give you a "why". Haven't used Shell in a really long time...Used to see a crusty residue on customers plugs that looked like a yellow shell around the electrodes and on the ground strap. Also mostly driving stuff with at least semi-hot rodded engines (even the last one, an old dodge dart with a 321 (non stock 318) 4bbl with a ton of suspension stuff done to it). Always ran the best Sunoco stuff available with something else added. (still miss the old 260). Lately I try to find anything with the lowest amount of ethanol and add acetone. Even my last car before Jeeps old chrysler fifth ave had an r/v cam set four degrees over, and suspension tricks.(just can't stop playing!
Anyhow...I think you are there...regardless of pressures. unless as I said, we missed something, but I really doubt it!!!
May 23, 2009
- Yup...Just got my nephew a deal on a 98 for $1700...he's had me out there putting in a new sound system, gps, radar detector,complete synthetic changeover. and now, since it's a little 4cyl, He is asking about engine mods to make it go faster...they don't really make much stuff for that but now he's thinking about a turbocharger (thank god they are really expensive,,,maybe he will change his mind!!!) he took it offroad the other day (right after waxing it) just to get it muddy. and cut down a tire it the same hole I split a trans line a week before in mine. Except for the smaller engine, his makes me a bit jealous!!! But it's his money and getting nearly a 4.0 in his first semester in college, how can I tell him no?
.Anyhow, let me know what goes on with it...need to learn something, especially since this has far exceeded the longest post I have ever went with in over 1800 ansawers I've given...Who Knew???
May 24, 2009
- Just noticed something interesting if you are going to rebuild. the 4.0 has the same bore size as the four cyl . BUT the 6 ahs 8something to 1 compression and the 4 has nine. If the wristpins are at the same height, you can get some free horsies from that. (well, not free, you need to get the pistons)
May 24, 2009
- Both have a 3.88" bore the 4cylo has 9:2:1 compression the 6 has 8:8:1. that's less but the 6 has a longer stroke (a bit more torque.) I'd have to check two things...rod journal diameter and rod length. also the actual location of the wrist pin in the piston In an ideal situation you could use the entire piston/rod assembly (Id need to get out my formulas to find out what that would make) But yes compression is horsepower (why there were never less than 11:1 pistons in my race engines.) Only thing of concern besides fit would be detonation. (I could not run a race engine on pump gas even the winter if I needed to move it out of the shop without it running on even without it being really warm.) with fuel quality somewhat more like good puppy pee, I wonder if it would cause a problem. (though the 6 has no problems) Next week I just may call the guys i used to deal with at manley and childs & albert and see what they think.
May 24, 2009
- Funny...was just thinking the same thing...must have gone to different schools together!
Jun 18, 2009
- Pump??? Pretty sure I mentioned that a bunch of times during this whole thing. Only thing missing was a "lock" on the diagnosis via some pressure readings. Chances are that with all the testing and cleaning up you have done, you have done a lot to prevent premature failure of the new unit...and if you are using OEM as a replacement perhaps you will have a far longer service life than you have been getting before. One thing though is try not to run below 1/4 tank...pumps need fuel around them to stay cool. (why I mentioned that I would rather modify the system to use an external pump and check valve...Mercedes did that for years and never had this kind of problem.). Funny that you posted today...was wondering how it turned out yesterday!!!
PS looked into piston and other performance mods to jeeps: turns out that cylinder walls are too thin to do anything meaningful there and only stuff available is expensive with no real dyno results to back up claims.Jeeps sure ain't chevies!!! Good luck with it!!!!
Jun 18, 2009
- Performance mods werent only for you...I can't stand driving anything that isn't somehow faster than it should be...Or for my nephew, who is now "stuck" with a four banger that runs perfectly but can't get up a long grade without dropping into a lower gear.
I hope to be here for a while but may wind up homeless soon...ex business partner is trying to take house away... long story but boils down to him being greedy and cheap, screwing me around on a verbal contract we had. Ran me out of money and I can't get a lawyer to help without funds...Wonder why no old lawyers don't offer help like we do on this site...sure would be nice!!!
Jun 19, 2009
- I don't know if you offended anyone but if you did, I hope it was a lawyer. I'm just so talked out on the subject that I don't have word for it anymore. Here's what it is: Several years ago I went into partnership with a friend and bought a bank foreclosure house (108 yrs old). He contributed about 50K for materials, I put in over 145K in labor (over 10,000hours. When nearly completed on the inside, he refused to do any work on the outside and completely cut off funding...agreement was that I live here forever and we start another house when this one was done. In January I learned that he not only cut off my funds but had not paid taxes for two years (nearly three. He is demanding that I pay him rent and claiming I am a "squatter" and is attempting to evict me (though I have papers showing I am an equal partner in LLC formed for the house.)
I've been on every website I could think of and have talked to so many lawyers that I could populate a small town with them.Same answer from all..."you have a great case but I can't represent you because you don't have any money" (all want at least 3K to even begin.) I've offered all to pay on back end as contingency. Truth is I don't even want the money anything I get I'll pay back taxes on and put the remainder into marketing an invention I have used in deer hunting (something I dreamed up back in 89 and have pulled bucks out of impossible places with ever since. (website http://www.x17deerslayer.com/test) we put up website but haven't advertised because the original backer pulled out at the last minute and we missed all ad deadlines. I don't want to sound crazy but it should produce at least 30mil in sales if done correctly (that's if we can sell to 1% of deer hunters in the US.) With all this stuff going on I am about to loose my mind so I do the fix ya thing to keep my sanity. I think I may have a backer, but all he want's to do is talk and I haven't seen any financing yet. My nephew thinks he is either trying to steal the thing or he is a "spy" working for my "friend" to keep tabs on me. I spent my entire life helping people and it is really sad that now it's like I'm alone in a field with really big rocks falling and no one is helping. Even the guy who backed out on me last year came away a winner...I built three rooms repaired all the plumbing and re-wired (including 200amp service panel) nearly every room to bring them to national code, in his daughters house where Lincoln's wife used to go to talk to ghosts (documented, in Moravia N.Y.) That dosen't include the windows I removed and doorways I built etc, And I spent the entire summer there overseeing an 80K grant renovation to the house exterior. I did this free!!! In New York City they would call me a ":shmuck" and perhaps I am. I can't say more here...I likely said more than I should but I'm at fishnhunt@hotmail.com if you need me for anything.
Expert
