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stumped on 96 fuel delivery

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Old 06-27-14, 06:08 PM   #1
4hunnit
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Default stumped on 96 fuel delivery

So I've got a 96 automatic. About two weeks ago I had a weird problem occur while driving - engine seemed to starve itself of gas, revs went down and wouldn't let me give it gas, until it finally stalled. So I went through a few things and ended up swapping my ECUs. Problem disappeared. For a day or two. Then it stalled a few times while driving but would start back up, until about two days ago. Starved itself a few times in the past few days, so I finally pulled the pump out (which I replaced just over a month ago) and gave it a manual jump, and she worked fine. Also replaced the fuel pump relay about a week ago, but I returned it after it did not solve my problems then. Now the part I am stumped on is that if I sit on the side of the road for about 45 minutes, the car will randomly surge fuel, and fire up, after it seems to cool itself down. Any ideas? Would this point to a shorting pump relay? Not sure if the coolant temp sensor would give it the effect of not surging the fuel pump?
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Old 06-27-14, 06:14 PM   #2
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Also, it was shooting me a code P0133 some days ago, and I thought that this model had a fuel pump resistor (it does not.. ). So I went under the hood, and bolted to the driver side wall, right near the battery and wiper fluid input, there's a metal "something" shaped like a rectangle. Silly me thought maybe this was the resistor, so I took it off, cleaned it up with contact cleaner, put it back in, and my code went away, therefore my CEL went off. Related in any way? No idea what it is or it's purpose.
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Old 06-27-14, 09:25 PM   #3
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Have you already changed all the capacitors in the ECU? If not, I'm willing to bet that is your culprit. It's actually something you should do or have done, as these capacitors WILL FAIL if they haven't already.
There is a huge thread dedicated to this subject already. Might be a good time to read up.

Here you go
http://www.clublexus.com/forums/ls40...capacitor.html
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Old 06-28-14, 03:21 PM   #4
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As above but also having changed both the fuel filter and relay have you considered a partially blocked fuel filter?
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Old 06-28-14, 04:51 PM   #5
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Quote:
Originally Posted by IBGREEZY View Post
Have you already changed all the capacitors in the ECU? If not, I'm willing to bet that is your culprit. It's actually something you should do or have done, as these capacitors WILL FAIL if they haven't already.
There is a huge thread dedicated to this subject already. Might be a good time to read up.

Here you go
http://www.clublexus.com/forums/ls40...capacitor.html
I haven't changed all of the capacitors, but two of them yes. But my reason to believe it may not be the ECU is because I have two ECUs. And both of them are not changing anything on the car. Of course, there's always the chance that both may be bad, but what are the odds of that being so? Even if they were both bad, I would expect them to at least start the car for a bit before starving it, but neither one of my ECUs will fire her up.
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Old 06-28-14, 04:55 PM   #6
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Quote:
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As above but also having changed both the fuel filter and relay have you considered a partially blocked fuel filter?
I changed the filter when I did the pump almost two months ago. This could still be an issue that I will check on in a few minutes. Now, if this is clogged, wouldn't the pump still surge? or will the pump stop itself once enough back pressure has built up, like a clog would do?
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Old 06-28-14, 04:57 PM   #7
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Also changed the pump relay again, and had my igniters tested at Autozone multiple times. And they passed all levels of the Wells test.
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Old 06-28-14, 06:14 PM   #8
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Fuel filter is perfectly fine, blew right through it. Gas is coming out clean as can be. Definitely a power problem with the pump itself. I had this come across my mind earlier - what's the likelihood of that positive wire (inside the tank on the pump), going bad? I mean I didn't notice anything off about it when I took the pump out earlier, the protective wrap around it was starting to be eaten away in a very small spot, but not exposing the wire in anyway, just showing the next layer of insulation. Not sure if it's worth pulling out again, and it's riveted into back of the access cap behind the seat. Just a thought, I'm running out of options here.
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Old 06-28-14, 07:29 PM   #9
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have you checked fuel pressure?
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Old 06-28-14, 09:22 PM   #10
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I figured fuel pressure was irrelevant here given that there's no fuel to reach that point of the car
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Old 06-29-14, 09:08 AM   #11
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How do you know if you haven't checked?
How much fuel pressure along with how you are losing pressure (if at all) will tell you what's up.
Did you at least depress the schrader on the rail to see if you had any pressure?


If you are not testing things, you are chasing your tail. You could have other problems other than fuel delivery... Without going through a methodical diagnostic, you are throwing darts at a map, hoping to hit the right town.
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Old 06-29-14, 10:21 AM   #12
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Quote:
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How do you know if you haven't checked?
How much fuel pressure along with how you are losing pressure (if at all) will tell you what's up.
Did you at least depress the schrader on the rail to see if you had any pressure?


If you are not testing things, you are chasing your tail. You could have other problems other than fuel delivery... Without going through a methodical diagnostic, you are throwing darts at a map, hoping to hit the right town.
I've still taken it into consideration. Me and my friend couldn't find the pressure release valve under the hood though. Also, this morning when I got up, she fired up. It's a problem with the pump not pumping at all. I can hear when it comes on, however it loses all power and refuses to juice up again, therefore starving the car of fuel. Usually when I go to start the car over the past three days, there's been no sound (no power) to the pump - it's not doing it's job. However, this morning, I had her idling for almost 20 minutes, then suddenly loss of power to the pump, and stalled of starvation. I understand that fuel pressure would cause starvation, but does it have any effect on the powering of the fuel pump? What I mean is, once a certain pressure level is reached, does it send a message to stop the pump from pumping, until more pressure is needed? If not then I believe that rules out the pressure.

Also, yesterday when I took off the fuel filter, I kept trying to "start" the car to see if it would at least spew fuel all over the ground, and still had no juice to it. My pump is under warranty, so I'm replacing today as well. Maybe it's just a short in the pump? Hoping so, wish I had used the OEM pump to begin with two months ago.
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Old 06-29-14, 11:45 AM   #13
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it's about following a method so you don't end up skipping something... you didn't make it emphatically clear that you did any flow/pressure tests, so i was just making sure. lots of noobs come on here and start posting stuff they replaced without checking anything...

I'm an almost 15year master tech, and it bothers me to see people spending money by replacing parts rather than spending time and diagnosing the problem and not wasting money.



check static line pressure
check primed pressure
check running pressure
check dead-head pressure

check flow out
check return flow

Check for proper ground from pump

test for power at pump on ACC
Check for power on crank
Check for power on running

test for power at relay on ACC
Check for power on crank
Check for power on running

Supply direct power and ground to pump and check pressures as above again

check wiring along entire fuel pump circuit (can be done by checking voltage drop, continuity or line resistance) at key breakout points and connectors.

if you don't have a DVOM or Multi-meter, get one.



Sure, you might have a faulty pump, it's not likely but it is possible. You could also have a used/dead pump somebody cleaned up and put back in the box and returned to the store after putting the good one back in their car. Seen that one a few times at parts stores. you could also have your connections backwards if you wired the pump yourself. simple pole-type pumps from cheap brands can often have the +/- switched easily...


you could also have an ignition switch problem, relay problem, wiring problem, connector problem, ground problem, power supply problem, wiring problem... Hell, i have seen guys hook the feed to the return on cars before... anything is possible. do you have any or at any time was there stereo upgrades like Subs in the trunk? I have seen cars where guys tapped into the fuel pump power as a remote turn on for an amp and other crazy stuff.

hopefully the new pump fixes it, if not start from the beginning and test like i just outlined and you will find the problem within 2 hours.
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Old 06-29-14, 02:18 PM   #14
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It was, indeed, the fuel pump. It would manually jump fine when I took it out both times and applied voltage to it, but the problem was that it would just cut itself out. Therefore my diagnosis of it wasn't giving me any results.. unless I had sat there for a couple minutes continually giving it juice. So I guess I kind of skipped right over that and figured it was alright if it ran the second I gave it live wires. My neighbor just chimed in from across the yard and told me to replace it even if I didn't think that was the problem. Thank god for him, saved me so much time and possibly money. I thought I was running out of options. Thanks guys though for the assitance, did help me learn a few things more about diagnosis.
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Old 06-29-14, 02:18 PM
 
 
 
 
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