Lexus082

Took my car to the shop because it would start but would stall out right afterwards. They came up with the same diagnosis as i did, being a bad fuel pump computer. So I purchased a used computer and swapped the computers out and it did not change anything. So then I went and found another 4fuel pump computers and they as well did not fix the problem. The shop I took the car to said that i needed to order a new fuel pump computer and that would fix the problem and they would have me back on the road for another $420 for the computer. But i find it very hard to believe that all five fuel pump computers are all bad. They never tested each computer, they just plugged it into the car and came to the conclusion that each computer was bad since it didnt fix it. Now there's a chance i have very bad luck and all the computers are bad. But i think its a very very slim chance.

What makes more sense to me is the main ecu is faulty that controls the fuel pump computer and I would much rather spend the money on a main ecu than add another fuel pump ecu to my collection. I asked the shop if the 'new' fuel pump ecu didn't fix the problem would I be stuck with the part and be out $420 bucks and they said yes. Do you guys agree that I should assume that one of the fuel pump computers is good and go ahead and replace the main ecu and possibly the wiring harness from the main ecu to the fuel pump ecu?

sj408

iTrader: (6)

Im not so sure about the sc400 but for instance on my 300 we bypassed the fuel pump ecu and wired it to 12vs. Basically comes on with the key on. I wouldnt spend 420 dollars on a fuel pump computer but sometimes if somewhere gurantees the diagnosis it might be worth it.

V8drummer

iTrader: (5)

You can bypass the Fuel pump ECU my bridging the correct two ports on the diagnostic box ( do a search to show which ones). That will tell you if the fuel pump ECU is the culprit or not. I hope they did that before getting 5 different ECUs.

ihiryu

iTrader: (7)

B+ and FP in the diagnostic port to bypass it

Lexus082

I did the fuel pump ecu bypass and it worked for about two weeks and then it started acting up again and stalled out on me even while the fuel pump ecu was bypassed. When I connect the b+ and FP in the diagnostic port it idles very poorly, misfires and the engine shakes. So that kind of told me it was the fuel pump ecu was bad, but when I tried several other fuel pump ecu's none of them keep the car running. The engine will start, but will stall out within a second. The shop said the fuel pump ecu that was in the car was bad along with the four or five other fuel pump ecu's I provided them with to test out. I find it highly unlikely that all of the fuel pump computers are bad. I think there's a better chance that the main engine ecu that controls the fuel pump computer is at fault.

After it started acting up I thought maybe it had damaged the fuel pump since it was running at high speed all the time. So I changed fuel pumps and that didn't fix the problem either. I'm not sure why I'm having a problem with this fuel pump ecu bypass when it seems like a common fix for many. The last day I drove it, I could just feel something wasn't right. I parked the car at the gas station and when I came back out to restart it, it wouldn't start it would just crank and crank and crank. Then after about five minutes I was able to get it started and drove a couple miles where it stalled out and was difficult to get it started again. So after another five minutes I was able to get it started and was able to drive about 8 miles, then I was going about 40 mph and the car started to accelerate on its own while I had my foot off the gas pedal. Like it was getting more fuel that it was suppose to. Then finally I pulled into the driveway and came to stop and the engine was revving up the idle in gear was increasing and was around 1500-2000 rpms and I just put it into park and turned it off. Thats when I re-wired it the was it was suppose to be and tried several different fuel pump ecu's.

Even though I obtained the replacement fuel pump ecu's from the local junk yards I'm pretty sure most of them if not all of them work properly because logically the cars ended up in the junk yard because of an accident most likely while they were being driven. So if I assume that the fuel pump computers or at least one is in good working order I would think it has to be what controls the fuel pump ecu that is messing up which would be the main ecu or possibly the wire harness that ties the two computers together. Or I'm completely wrong and all five fuel pump computers are bad. I just find that very unlikely, even the mechanic was surprised none of them corrected the problem. I just think my current problem is somehow related to the fuel pump ecu bypass.

ihiryu

iTrader: (7)

When you do the bypass it bypasses the fuel pump ecu all together. I've had mine bypassed for a long time with no problems.

Have you checked wiring? Or even the fuel filter? Toyota claims it's a lifetime filter, but if that's the case, why do they make replacements?

Lexus082

Yes, before I found out it was the fuel pump ecu, I changed out the fuel pump, fuel filter, spark plugs, wires, caps & rotors. The engine would start but would stall right out. And then I used a paper clip and connected b+ and Fp and the engine started and continued running. I was so relieved after months of not having the car on the road. So I did the fuel pump ecu bypass and clipped the two wires and connected them together and taped everything up.

The bypass worked for about two weeks. I was coming off the highway one day was drifting slowly to the red light and the engine stalled. It took a little longer than normal to get it started, but it did start back up and I made it to work ok. After work I headed to the gas station and the engine was hesitating really bad. I made it to the gas station and when I went to leave the engine wouldn't start, it just continued to crank. Finally after five or ten minutes it finally started up and I was able to drive a couple miles before it stalled out. It was difficult to restart the engine again, but after a few minutes it started up and I was on my way. And about a mile before I made it home, that's when the engine started to accelerate on its own.

All these problems occurred while the fuel pump ecu was bypassed. So I parked the car and the next day it started up but it was misfiring at idle. So that's when I re-wired it back to normal and tried a different fuel pump ecu which didn't correct the problem, so then I tried four other fuel pump ecu's and they didn't fix the problem either. So being very frustrated I called a shop to tow the car and diagnose it. Their diagnosis was the fuel pump ecu was bad. I also gave them the other four spare fuel pump ecu's to try out and they said all the those fuel pump computers were bad as well. But when I talked to shop it sounded like they just tested the pump computers by plugging in each one.

I just don't know why all of a sudden the engine is misfiring and stalling when the ecu is bypassed. Along with the engine increasing in speed causing the car to accelerate and increase in speed when my foot is completely off the gas pedal. And when I was in the driveway with the car in drive and my foot on the brake the engine was idling in drive around 1500-2000 rpm's. I just don't know if its just a coincidence and I'm having a new problem now along with a bad fuel pump ecu. I'm just afraid if I order a new fuel pump computer like the shop says I need, it wont fix the problem and I'll have another one to add to my collection. Again I just find it highly unlikely the five fuel pump ecu's I have acquired are all bad.

I was thinking of having the car towed back to my house, replace the wire harness that runs from the main ecu to the fuel pump ecu and replace the main engine ecu that controls the fuel pump computer.

I'm not sure if the tech tried bypassing the fuel pump computer, but I'm going to talk to him and hopefully maybe he can at least tell me what is causing the engine to misfire when the fuel pump ecu is bypassed when using the jumper wire between B+ and Fp.

ihiryu

iTrader: (7)

At this point it does sounds like the main ecu has gone bad, I highly doubt it's the fuel pump ECU.

sj408

iTrader: (6)

You sure its not just the fuel pump itself as well??? i had a bad fuel pump a couple weeks ago, it would stall out and run like it had bad plugs or a bad tps for small periods of time. Alot of hesitation as well it would bogg horribly in lower rpms.

kmoore737

Hey I am new but I cannot find the procedure to bypass the fuel pump ecu nor can I find the instructions to test mine....anybody lead me in the right direction?

kmoore737

Disregard...I found the procedure

shonuff53

iTrader: (3)

so while I'm on here... I'll say that I've fixed a few of these problems on several different model Lexus' you're all correct about what it is sometimes its only an ecu or wiring or both. Easiest way to check it is to run about a 12 gauge wire or 10 all the way to the rear connector by the pump and see if that bad boy comes back to life. Sometimes the wiring from that rear connector to the pump can be bad these are all easy to check using your volt meter. If the bypass didn't work and you're getting low voltage at the pump its time to wire your own relay and 10 gauge power and ground you can tee off of your original fuel pump 12v source at the fuse box and you won't need a relay or you can hook up your own relay and use ignition or something as your reference to cut relay on. Keep in mind straight power with no easy off could be a fire hazard. Review some basic electrical information have a good idea whats going on before ruling out anything or installing anything don't forget to cut power before messing with wires in a fuel cell just saying cause people do it all the time.

CHIKARA

So what happened! Have same problem!!!!aaaaaaaaaaaaaaaaa

Brianmoss

Same here want to see what the end result is

DVSBSTD

I have the exact same problem and wanted to know if it was intact the fuel pump ecu before I go an waste more money trying to fix other things on the car, thanks