KO Posted April 28, 2008 Report Share Posted April 28, 2008 98 Wrangler Sport 4.0L. Hard starting when it's set for a while, have to crank on it once, let off, crank on it again, sometimes 3 times, and then when it start it stumbles around then the idle smoothes out. Only does this when it's set up for a while. I'm assuming it's surely the fuel pump or filter. From what I've learned the pump/strainers are all in the tank. I've looked up fuel pump assemblies and there are about 50 options. Anyone ever replace it before, if so what did you use? They range from a pump with strainers for $120 to a complete "module" and strainer for $260. Link to comment Share on other sites More sharing options...
Minagera Posted April 28, 2008 Report Share Posted April 28, 2008 98 Wrangler Sport 4.0L. Hard starting when it's set for a while, have to crank on it once, let off, crank on it again, sometimes 3 times, and then when it start it stumbles around then the idle smoothes out. Only does this when it's set up for a while. I'm assuming it's surely the fuel pump or filter. From what I've learned the pump/strainers are all in the tank. I've looked up fuel pump assemblies and there are about 50 options. Anyone ever replace it before, if so what did you use? They range from a pump with strainers for $120 to a complete "module" and strainer for $260. Funny you ask. I have a 97 Cherokee I just did that one. I went down to Napa and got the $140 kit. It has the strainers and the pump, which happens to be a walbro. Took me about an hour to do it all. Honestly it might be the pump, but I would guess it is probably ignition. Seafoam that bad boy :-P Link to comment Share on other sites More sharing options...
KO Posted April 28, 2008 Author Report Share Posted April 28, 2008 Well I suspected ignition at first so I put brand new spark plugs in it. I really feel like it's the pump or filter because of the way it runs rough after it initially starts then it smooths out, I think it may be a partially blocked strainer or dying pump, seems to be getting worse too. I'll have to go down to NAPA and check out that kit. Thanks. Link to comment Share on other sites More sharing options...
Minagera Posted April 28, 2008 Report Share Posted April 28, 2008 (edited) I tell you, it really was easier than expected. I just dropped the straps down as far as they would go without actually unbolting them disconnected the 3 items on top; Pump harness, vent tube, supply since your pressure regulator is in the tank. Then drop the tank and go man :-) EDIT: http://www.jeepforum.com/forum/showthread....;highlight=fuel Cherokee link or How To, but generally the same. Edited April 28, 2008 by Minagera Link to comment Share on other sites More sharing options...
Casey_L Posted April 28, 2008 Report Share Posted April 28, 2008 replace the IAC (idle air controler). Its a $40 part attached to the throttle body with two torx screws. Should be facing the firewall. Does your engine sometimes idle a little lower then it should? Then it is the IAC. Link to comment Share on other sites More sharing options...
Shelby Posted April 28, 2008 Report Share Posted April 28, 2008 or it might be a simple thing like the fuel pressure leaking down to "0" and once the pump is trigger'd ithas not enought voltage to instantly build up pressure,,a simple test for this is to cycle the ign on 3-5 times with out hiting the starter,, alowing the pump to run the 1-2 sec durring the key cycles , now be sure the pump is doing the pre run ,the ecu controls the pre run time to prime the system static pressure on the fuel system is control'd by the pressure reg and the leak down valve in the pump , eather or both can cause a pressure leak down,, but those pumps are a know failure problem,,every one i know with one has done at least one pump some injs will not open even with the proper electrical signal if there is not a min amount of fuel pressure Link to comment Share on other sites More sharing options...
Truth Posted April 28, 2008 Report Share Posted April 28, 2008 now Keith, you can't just come around here and start asking questions without saying "hi" first! Link to comment Share on other sites More sharing options...
Turborusty Posted April 28, 2008 Report Share Posted April 28, 2008 IAC is my vote as well. Could be pressure bleed off as well.........but I've sen tons of carboned up IAC's A good cleaning will usuaaly get them freed up unless the adjustment motor went kaput. A plugged strainer or weak pump will show it's problems under load typically. Turborusty Link to comment Share on other sites More sharing options...
Laodicea Posted April 29, 2008 Report Share Posted April 29, 2008 It is the stupid resistor ballast. The white thing above the fenderwell on the driver side under the hood.....just make a jumper wire for it. If this is the same as my 4.0 L jeep cherokee. When it warms up it creates resistance and makes it hard to start. It is there to reduce the voltage to the fuel pump....I think you need all you can get. Link to comment Share on other sites More sharing options...
Shelby Posted April 29, 2008 Report Share Posted April 29, 2008 man thats a little old school isn't it,, i haven't seen any system still useing a ballist resistor in years one thing about most of those systems is you need'd a bypass resistor circirt durring start up,,this runs full 12 volts to the ign system durring start up for increase'd ign voltage out put,, once the starter is no longer operateing the voltage drops back to the value regulate'd by the ballist resistor older fords with 2 wire solonid, and chyr dual resistor ign systems are a couple that did that Link to comment Share on other sites More sharing options...
Laodicea Posted April 29, 2008 Report Share Posted April 29, 2008 man thats a little old school isn't it,, i haven't seen any system still useing a ballist resistor in years one thing about most of those systems is you need'd a bypass resistor circirt durring start up,,this runs full 12 volts to the ign system durring start up for increase'd ign voltage out put,, once the starter is no longer operateing the voltage drops back to the value regulate'd by the ballist resistor older fords with 2 wire solonid, and chyr dual resistor ign systems are a couple that did that it might be mine is a 1990 Cherokee....but I am not sure when they quit using them....I saw so many people having problems with them...took me like 4 months to figure out why i couln't get the stupid jeep to start when I parked it washed under the hood...then that was it for months....ballast resistor got wet and terminals turned green...no start.... Changed all sorts of things....fuel pump assemble...checked all wires fuses..relays...coil..it was that after i wiggles the connections it started....took me weeks of reading on the xj jeep forums. Link to comment Share on other sites More sharing options...
Shelby Posted April 29, 2008 Report Share Posted April 29, 2008 humm about time for a coil spark test huh Link to comment Share on other sites More sharing options...
SQF Posted April 29, 2008 Report Share Posted April 29, 2008 My 1993 also had the ballast resistor. I wouldn't think failing pump or clogged strainer, like Rusty said, it would present more under load if it was having problems supplying the fuel. Link to comment Share on other sites More sharing options...
KO Posted April 29, 2008 Author Report Share Posted April 29, 2008 LOL, yes I should say hello before just using everyone for their knowledge. I will have to check into this IAC then, yes there are no problems under load so that does sort of point away from the pump/strainer I suppose. Link to comment Share on other sites More sharing options...
Shelby Posted April 29, 2008 Report Share Posted April 29, 2008 any air leakage can effect the IAC and the fuel mix,, check any and all vent and vac hoses, doesn't that eng have a 2'd hose on the pcv valve hose,,i have seen them slip and draw fresh air into the intake after the t-plate , air with out fuel can cause poor starting cold but when hot it don't make that much diff cauese the engine is warm needing less fuel to idle Link to comment Share on other sites More sharing options...
Turborusty Posted April 29, 2008 Report Share Posted April 29, 2008 Yup Shelby...Had this same problem with my last 5.9L Dakota. The AIC got carbon built up on the piston and would not close fully, it was allowing excess air in on cold startup making it hard to start. It would also try to stumble a little pulling away from a stop, until it warmed up fully. Can't say for certain this is it, but it's a good place to start looking. Turborusty Link to comment Share on other sites More sharing options...
KO Posted April 30, 2008 Author Report Share Posted April 30, 2008 I sprayed all the hoses while it was running to check for an air leak and also pulled the AIC. It had carbon built up on it but nothing wd-40 and a light wire brush couldn't take care of. Cleaned it up real nice, made sure the piston in it was popping in and out just fine and installed, same thing. It may just be me but it seems if I pump the gas pedal 6-7 times before I attempt to start it then it will fire up quicker. Link to comment Share on other sites More sharing options...
Shelby Posted April 30, 2008 Report Share Posted April 30, 2008 KO did you try the ,multi cycle the key on and off, if so that will elim the low fuel pressure thing as a cause for slow starting , also my nephew has one of them but i can't recall if it has an air mass or not , also check the CTS, most late model systems use a doubble inj pulse to aid in starting a cold engine,, but only if it gets the proper signal Link to comment Share on other sites More sharing options...
KO Posted April 30, 2008 Author Report Share Posted April 30, 2008 Will do shelby, thanks for the advice I appreciate it, need to get this taken care of so I can get rid of it and buy the wife something more economical. Link to comment Share on other sites More sharing options...
Chad Posted April 30, 2008 Report Share Posted April 30, 2008 Why fix it, just make sure it's warmed up every time you show it to a buyer of trade it in... Link to comment Share on other sites More sharing options...
KO Posted April 30, 2008 Author Report Share Posted April 30, 2008 LOL Link to comment Share on other sites More sharing options...
Lusion972 Posted May 1, 2008 Report Share Posted May 1, 2008 Why fix it, just make sure it's warmed up every time you show it to a buyer of trade it in... :iagree: Just didnt want to be the first one to say it Link to comment Share on other sites More sharing options...
Chad Posted May 1, 2008 Report Share Posted May 1, 2008 :iagree: Just didnt want to be the first one to say it Yah, it's a "tool" thing to do to someone, but you wouldnt be the first... Link to comment Share on other sites More sharing options...
KO Posted May 1, 2008 Author Report Share Posted May 1, 2008 Well, I multi-cycled the key to the on-off position about 5 times then turned it over, it started much, much easier, I'm thinking it's definitely the fuel pump. Time to run it low on gas and drop the tank. Thanks for all of the help. Link to comment Share on other sites More sharing options...
Shelby Posted May 2, 2008 Report Share Posted May 2, 2008 not so dang fast ,, no one said the fuel pump was bad,, that is just a first step in trouble shooting,,now weget out the pressure gauge and do some system pressure tests,, your looking for a leak down from the pressure reg or the one way valve at the fuel pump out let,, or a leaking inj first build up pressure and see if it realy is going to 0,, and how fast it is doing so,, now pinch off the return fuel line and redo test,( your now testing the fuel pump check valve),if pressure still drops quickly,,repeat the test and while system is still at pressure pinch off the main fuel line ahead of the fuel pressure gauge, (now your checking the injs ) to test the pressure reg for leak down,, pinch off the supply line ahead of the gauge be careful not to damage the rubber fuel hose with luck it won't have them darn plastic fuel lines Link to comment Share on other sites More sharing options...
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