View Full Version : Fuel System Issues?
Got a new to me 2001 Vx (see 2001 in Florida... under vehicles for sale). Picked it up from a dealer in FL to drive to Austin, TX. Around a hundred miles into the return trip I started having trouble. :( The Vehicross started bucking severely under acceleration and I eventually got an engine code for low voltage on two O2 sensors. I first found some loose battery connections and reseated/tightened those but that just cleared the engine codes temporarily and the bucking under acceleration came back. Limping into Bradenton, FL for the night, I went to a Pep Boys there on Saturday. They found low pressure in the fuel line (30 (psi?) versus the recommended 50+) and replaced the fuel pump. On Sunday I was able to make it back to Austin, but it was painful.
Unfortunately I'm still having a few issues and I need help identifying the culprit:
1) After about an hour of driving the vehicle starts bucking again (thinking maybe there is a vacuum getting formed in the fuel line?) My temporary solution is to gas up every hour or so. This was tedious on a 20+ hour trip but for the hour after filling up the vx ran great.,
2) My fuel gauge is all over the place. Perhaps this is related to #1, or perhaps the sending unit on the fuel pump also needs to be replaced?
Thanks for your help!
JAMAS
04/18/2011, 11:20 AM
2) My fuel gauge is all over the place. Perhaps this is related to #1, or perhaps the sending unit on the fuel pump also needs to be replaced?
This seems to be a common thing. My gauge is great after fill up, then it bounces around a little. I would not think the two are related, but anything is possible. I believe I recall reading that the sending unit has often been the culprit.
Was there a warranty provided by the dealer?
Was there a warranty provided by the dealer?
Yes, a limited warranty that covered the fuel pump replacement. Hopefully it'll cover some of the other work that needs to be done...
VX KAT
04/18/2011, 11:32 AM
maybe a dumb question, but did you replace the fuel filter as well? I know that caused bucking in another car I had.
did you replace the fuel filter as well?
No, but looks like the dealer already replaced it as its quite new -- I'd guess less than a month or two old. Think I should go ahead and replace it?
VX KAT
04/18/2011, 11:42 AM
No, but looks like the dealer already replaced it as its quite new -- I'd guess less than a month or two old. Think I should go ahead and replace it?
...could they have lied about replacing it? It's such a cheap item, I'd replace it again. With the bucking stopping when your tank is full, I have to defer to the more experienced gang here.
Hope it works out for you, I know this takes away from that new car giddy feeling...but it should be resolved pretty soon I'd think.
I'd replace it again
Roger that.
With the bucking stopping when your tank is full, I have to defer to the more experienced gang here.
Yes, thats the part I can't quite figure out, thinking that maybe filling up is breaking a vacuum on the tank. What sorts of emissions hardware is there on the VX? Perhaps something is plugged?
Hope it works out for you, I know this takes away from that new car giddy feeling...but it should be resolved pretty soon I'd think.
Yes, its been a long few days. Looking forward to getting the vx up and running like a champ.
Y33TREKker
04/18/2011, 12:37 PM
Low pressure on the fuel line could have also been caused by the Fuel Pressure Regulator being faulty, which is a common problem on VX's. A relatively easy replacement cost/procedure too. Irregular fuel pressures from a faulty FPR could have also caused the low voltage readings responsible for the codes you were getting from the O2 sensors.
I don't know exactly what goes wrong with the stock FPR's on VX's, but given the mileage on the one you purchased, it's likely that the original is still in place, so it would be a likely place to start.
Congrats on the purchase, and welcome to the site. :thumbup:
Low pressure on the fuel line could have also been caused by the Fuel Pressure Regulator being faulty, which is a common problem on VX's
I don't know exactly what goes wrong with the stock FPR's on VX's, but given the mileage on the one you purchased, it's likely that the original is still in place, so it would be a likely place to start.
Okay, sounds like a good thing to replace in any case. If the FPR is the problem anyone have ideas on the mechanisms whereby it'd cause the issues I'm seeing (how would refueling get the FPR working right for an hour)?
Congrats on the purchase, and welcome to the site.
Appreciate it. :)
tom4bren
04/18/2011, 12:57 PM
Have them clean the MAF as well. Those symptoms were very similar to some problems I had when I first got mine (including running better with a full tank).
MSHardeman
04/18/2011, 12:59 PM
FPR replacement how-to:
http://www.vehicross.info/forums/showthread.php?t=12021&highlight=fuel+pressure+regulator+replacement
I used Dino's instructions and got the fuel pressure regulator replaced in not time with minimal knuckle damage.
Have them clean the MAF as well.
Will do.
FPR replacement how-to:
Excellent.
Y33TREKker
04/18/2011, 04:09 PM
Okay, sounds like a good thing to replace in any case. If the FPR is the problem anyone have ideas on the mechanisms whereby it'd cause the issues I'm seeing (how would refueling get the FPR working right for an hour)?
FPR's on VX's are well known to be inhabited by irrational/irregular problem causing mechanical demons who operate under time-frames exhibiting no rhyme or reason. Historically, that's been the most regularly documented mechanism for issues on VX's like the one you're experiencing that have turned out to be FPR-related anyway.
Or in other words...not a clue. :bgwo:
etlsport
04/18/2011, 05:54 PM
are you sure its filling up that helps the problem? could it be just having the vx turned off or opening the gas cap?
I remember when my FPR went, i would have starting issues, but if i opened the gas cap it would hiss, and things would work better, def try that
Cleaned the MAF. That was easy.
FPR's on VX's are well known to be inhabited by irrational/irregular problem causing mechanical demons who operate under time-frames exhibiting no rhyme or reason.
Haha.
are you sure its filling up that helps the problem?
turned off isn't doing the trick.
could it be just having the vx turned off or opening the gas cap?
could be, but did try driving with cap loose to no avail. that is kind of my line of thought.
I remember when my FPR went, i would have starting issues, but if i opened the gas cap it would hiss, and things would work better, def try that
will do.
Riff Raff
04/18/2011, 06:31 PM
I'm wondering if it could be more related to voltage/spark/electrical problems, and not related to fuel issues??? Hope you find the gremlin(s).
Dmitrikr
04/18/2011, 07:26 PM
Have them clean the MAF as well. Those symptoms were very similar to some problems I had when I first got mine (including running better with a full tank).
got four Isuzus last year in the shop with codes for both O2 sensors. But the problems were - MAF sensors on two; on other two-someone forgot to tight the clamp at air intake hose to plenum - created air leak not counted by MAF sensor
I'm wondering if it could be more related to voltage/spark/electrical problems, and not related to fuel issues??? Hope you find the gremlin(s).
Will keep my eyes open -- known problem areas? Thanks.
got four Isuzus last year in the shop with codes for both O2 sensors. But the problems were - MAF sensors on two; on other two-someone forgot to tight the clamp at air intake hose to plenum - created air leak not counted by MAF sensor
Interesting. I did notice that a hose clamp was loose (now tightened) near the engine when cleaning the MAF today.
Bob Barker
04/18/2011, 09:18 PM
It makes sense that if you were gaining air after the MAF it could take time to set off a code from the O2 sensor reading a "lean" (very dangerous) burn in the exhaust after an amount of driving. The car is adding a set amount of fuel to be burned with an expected amount of air that is actually greater than expected.
Did you have a chance to drive around with the air leak fixed yet?
Did you have a chance to drive around with the air leak fixed yet?
Yes, I've driven it some and its running well. Really need to go on a one to two hour drive though. Hopefully I'll get a chance to do that later this week. Maybe I'll change the FPR first too.
After cleaning the MAF sensor, tightening a hose clamp, and driving the vx around for a few days the bucking has returned. :( Guess I will be replacing the FPR next.
samneil2000
04/21/2011, 07:54 AM
After cleaning the MAF sensor, tightening a hose clamp, and driving the vx around for a few days the bucking has returned. :( Guess I will be replacing the FPR next.
Sorry you're having so much trouble. I hope the fpr is your problem. Make sure you have or make the short allen wrench. It makes the job way easier. More or less impossible without it...
Y33TREKker
04/21/2011, 09:38 AM
Something else occurred to me given the fact that the symptoms seem to reappear after you've been driving for awhile, and that is whether your u-joints could be involved. I don't know how likely that is, because as much driving as you've done while the problem has been happening, you'd think that if a u-joint was seizing due to lack of lubrication, it would have just totally let go and broken by now, but then again, they're built solidly for a reason so...???
Easy enough to stick some grease in them anyway, and unless everythings' been lubed in the last few months, it probably wouldn't hurt regardless.
Sounds like quite a few possible culprits have been eliminated though, so with a little more patience, it surely won't be that much longer before you get it figured out.
Dmitrikr
04/21/2011, 08:07 PM
After cleaning the MAF sensor, tightening a hose clamp, and driving the vx around for a few days the bucking has returned. :( Guess I will be replacing the FPR next.
try to calculate the air volumetric efficiency (http://en.wikipedia.org/wiki/Volumetric_efficiency)before changing anything.
at least you can eliminate MAF, air leak, cat converter clogged problems.
explanation how to calculate efficiency (http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm)
Bob Barker
04/21/2011, 08:09 PM
What about the fuel cap? Is it gone bad? Mom had a bad fuel cap that would cause her driving issues in some other vehicle when I was younger.
And the winner is the Fuel Pressure Regulator! Thanks for the help everyone! No more bucking. :)
Bob Barker
04/27/2011, 09:37 PM
Yaaayyy for solutions!!!!
Got this followup question recently:
Just curious, did swapping the FPR fix your gauge needle jumping around?
Heres my reply:
Nope that required changing out the in dash fuel and temp gauge unit ( p/n 8972114670 as seen here http://www.catcar.info/isuzu/?st=50&l=bT09dXNhfHxjYz09Vlh8fHNuPT04fHxhbXNpZD09Mnx8Zm49 PTIxfHxuaT09MDI%3D ). Took a few months to get the part in and think it had a $200 or so cost. I've seen on the forum that sometimes tightening a screw for the gauge behind the dash can fix the jumping needle.
You could also have a bad sending unit, but I had to get a new fuel pump and sending unit too, and those didn't fix my bouncing fuel gauge.
djmdma02
07/10/2011, 06:15 PM
Got this followup question recently:
Just curious, did swapping the FPR fix your gauge needle jumping around?
Heres my reply:
Nope that required changing out the in dash fuel and temp gauge unit ( p/n 8972114670 as seen here http://www.catcar.info/isuzu/?st=50&l=bT09dXNhfHxjYz09Vlh8fHNuPT04fHxhbXNpZD09Mnx8Zm49 PTIxfHxuaT09MDI%3D ). Took a few months to get the part in and think it had a $200 or so cost. I've seen on the forum that sometimes tightening a screw for the gauge behind the dash can fix the jumping needle.
You could also have a bad sending unit, but I had to get a new fuel pump and sending unit too, and those didn't fix my bouncing fuel gauge.
Just my two cents... My fuel gauge is never right on (except at full) and I have no other problems (except a check engine light for the gas cap). :)
Tonight my low fuel light came on. After driving 5-10 more miles, a light bucking returned for the first time since 2011. Filling up the gas tank fixed things right up. I only had to put 20.5 gallons into the VX, so presumably I had 2 gallons of gas still in the tank. I'm wondering if perhaps my fuel pressure isn't quite right. Is there an adjustment for our FPRs?
evillecutter
01/24/2013, 07:51 AM
replacing fuel pressure regulator, idle control valve, and throttle position sensor fixed this problem for me (i also replaced my spark plugs and fuel filter at that same time) - no idea which one was actually the culprit but they all work together anyways as well as being fairly inexpensive and extremely easy to replace - or it could be intake manifold gasket leaking
Some good thoughts there.
Perhaps this is related: I've also noticed that when off-roading my air filter gets filled with dust quickly here in TX leading to the Vx losing power / dying / not starting until the air filter is blown out or changed.
Thoughts?
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