CIGLexus

iTrader: (1)

I hate to ask stupid questions, but I am hoping the community may have some insight on something I overlooked. My old 01 GS I have to my brother years ago stopped running one day. I have overlooked the issue for years as it has been sitting since then.

History

- Stopped running one day
- When I tried to start it after a month, started up for few seconds then died
- Assumed it was out of gas, put more, no start
- He took it to a shop who replaced "a bunch of stuff" but couldn't figure it out would start one day and not the other but always quickly die
- Towed it to his apartments, where it has been for now 2 years

Recent checks:

- Manual power to fuel pump turns it on (it does turn on) WHIZZZ sound
- Power to +b, and M-rel on ecu
- Power to fuel pump computer and on the output side (blue wire red stripe)
- Main relay works
- Security passes (key)
- Basic obd scan shows no issues, but its just a cheap scanner

I am starting to suspect the fuel pump computer or a very sick fuel pump. When it does start for 2-3 seconds it starts up clean but it dies a slow death as if it is either starving for fuel or air. When I hard wired the fuel pump to on it started promptly but died soon after I believe because it was giving now TOO MUCH fuel without the fuel pump computer on a returnless system. You could smell the richness from the tail pipe.

My main problem is that I do not have a place to work on it or check it, other than the apartments where it is parked and people look at me sideways.

So let me know what you think. When I get to the car again I do not have much time to play with it and he can't afford a shop to work on it. I know I am missing something but it has been many years since I have played with the Lexus side of things.

PS. If anyone has a fuel pump computer I can borrow, that would be awesome!

Yri

I believe there was a way to check resistance of the fuel pump using a multimeter. I think you put one end on the terminal 1 and then the other end on terminal 5 (at the fuel pump connector) and then set your multimeter to Ohms, then see the resistance. It should be between 0.2 ohms and 3.0 ohms. Here's a video of the entire procedure. It could also but the fuel pump computer too, though haven't seen that issue around too often.

kevin3344

Thanks for the video, I've always done it the old fashioned way by spraying starter fluid in the intake lol.

OP a Lexus mechanic can tell you or the dealer (if you can tow it there) for the cost of the diagnostic fee. My guess is the fuel pump failed. Not sure why the shop replaced a bunch of stuff if they didn't know what the problem was.

Bykfixer

Check the fuel line going into the tank for perferations. Every so often a line gets cracks in it that causes air to get sucked in instead of gasoline when the volume gets low.

kevin3344

Exact same thing happened on our 2IS. Take off the intake so you have access to the throttle body. Start the car and spray a little starter fluid when it starts to die. If it picks back up every time you do that, it means it's not getting fuel and that points to your fuel pump.

KyleH

iTrader: (1)

I have a spare fuel ECU, but you don't need that to verify the pump is the culprit or not.

Simply understand this - At your pump, the plug has 4 or 5 wires that feed the top of the hanger. Disconnect this plug. 2 wires are for power, the rest are for signal / gauge and inconsequential to the pump running or not. Take note of the the two thick blue wires and the pins they connect to at the plug of the pump housing. They are your power and ground. Blue with red stripe is power, blue with yellow/white stripe is ground. Get you a +12v source and hook it up to the + pin and ground the other to the chassis somewhere nearby and you'll immediately know if your pump is working or shot. If you're not hearing the pump run with the proper pins connected to 12v and ground, the pump is bad. If you hear the pump run when you make connection with these pins, have someone attempt to start the car at the same time and if it starts, I would suspect the fuel ECU (unlikely IMO).

I can give a more detailed analysis of the ECU pinout if you need it, but the above is far simpler for trouble shooting.

CIGLexus

iTrader: (1)

Ok further tests. I pulled up the fuel pump computer wiring diagram and the voltages that it should be putting out.

Fuel pump computer receives +12v and grounds properly.
FPC (the output to fuel pump computer, is proper 3V+ cranking) (This can range from 1.5V to 5V during normal operation)
FP+ (voltage output from fuel pump computer to the pump) at 10V during cranking . (This can range from 9v-12v during normal operation)

So it would appear that the fuel pump computer is working fine.

I did the resistance check on the fuel pump FP+ and FP- and I get nothing. In fact it is showing continuity between the 2 which should be a very bad thing. Thank you YRI for reminding me to check this. I refused to believe that the fuel pump would be bad, especially since it does operate when +12V is applied. Still, maybe something is very wrong with it which could explain the erratic behavior.

I found a good working used unit for $50 close by, so I'll change that and see how it goes. Thanks guys!

Yri

Sure, no problem. When I tested mine, I got about 1.2 ohms, which proves to be a good reading. Too little resistance is bad, and too much also means bad (just like the specs I posted). Keep us updated!

CIGLexus

iTrader: (1)

Actually I was wrong, I had Ohms on the wrong setting. I put it on the 200 setting and I get 0.6.

But what about there being continuity between the 2 terminals? It shouldn't do that should it?

Yri

There should be continuity, albeit with resistance. 0.6 Ohms means your fuel pump is still good, and if your fuel pump computer is fine, I'd suspect you should inspect for spark. If you check for codes (you must read with the key in the ON position), check for any P1300 codes. That code will cut fuel to the engine after it discovers an igniter circuit failure. This can mean the car will start for a few seconds, sometimes sputtering like it wants to start, but then not.

CIGLexus

iTrader: (1)

I have always had spark. No codes, but my scanner is very basic. When it does start, it idles smoothly then sputters as if it was out of gas.

When I had the fuel pump at full 12v, it would idle longer but eventually sputter and very rich smell from tailpipe as if too much gas.

KyleH

iTrader: (1)

I need a little more information:

Are you working with 2 yr old gasoline? If so, I'm surprised it starts at all. And frankly have far less confidence in your pump than the fuel computer. While I don't recommend it, rockauto has pumps for as cheap as $30-$40 if money is that tight.

Running the pump at a full 12 volts at idle could possibly make it run rich, although in theory, the fuel pressure regulator in the tank should be dumping all the extra fuel you don't need to keep the base pressure consistent at idle even with the full 12 volts. Did you run the test on the pump like I mentioned - direct wiring the +12v and ground? How long did it idle before it choked out?

Yri

Also, side note, if you ARE working with 2 year old gasoline, there are drain bolts on the bottom of each side of the fuel tank if you want to drain it out. It also may be a good idea to take the fuel pump out and inspect the filter as well. If the filter is clogged, the engine will use all the fuel in the fuel rail but have no supply since the filter is clogged.

CIGLexus

iTrader: (1)

I haven't had a problem with old gas in dozens of other toyotas sitting for years (here in Cali), but it was just about out of gas anyway so I put some in. I have the replacement pump handy now.

BUT now that I think of it, I did not put 12 volts properly, I did it with the FPC still attached. Now that I have the wiring diagrams I can put a proper +12v to the pump and try it before I change it out. I was under the impression that the FPC controlled the fuel pressure. Now that I have seen the pump replacement process and the FPR is inside the assembly, then you are right it should run fine at +12v.

PS. I tried to start it fresh today and it started up for about 5 seconds then slowly sputtered out (even with more gas in it.

I'm starting to wonder now if they messed up the firing order or timing when they were dicking around with it. When it does start it does not respond to throttle at all in fact hitting the gas makes it die faster.

So I will try 12volts today without the FPC and see what that does but I suspect it will be the same.

Yri

You have a point. An off-timing car will generally sputter or sometimes not start at all, and since these cars are VVT-i, the computer tries to adjust the timing itself (either retarding or advancing) and depending on which way your timing is off, it will eventually cause the engine to die. Also, if you mess up the firing order, it will fire misfire codes. So, if there are no codes, it's unlikely they had messed up the firing order. Check for yourself, all that's needed to be removed is the top timing cover.