Fuel pump is not priming the 2-3 sec before start.
07-11-18, 01:48 AM
#1
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Thread Starter
Fuel pump is not priming the 2-3 sec before start.
Help! My car cranks longer than it should to start. I recently changed the fuel pump and the fuel pressure regulator. Still having intermittent hard starting. I checked to see if there is voltage going to the pump when the start button is pushed in the first time (or the second time), when it should be priming for 2-3 seconds then turning off. Nope. No voltage, but when I put my foot on the brake and push the start button, I do get 11+ volts and you can hear the pump turn on. Eventually the car starts.
It seems to me the pump is working ok, but for some reason it is not getting a signal to prime (turn the pump on for 2 or 3 seconds, then off) when the start button is pressed with foot off the brake.
I have read other posts on the forum for other vehicles that had same issue with no conclusions other than it may be the ECM. Are there any other relays that could be a problem? I do not have a schematic nor know which other, if any, relays to check. I already swapped the Fuel Pump Relay and Start Relay in the engine fuse box to see if any changes, it didn't seem t make a difference. Not sure what to do at this point. Any suggestions?
It seems to me the pump is working ok, but for some reason it
I have read other posts on the forum for other vehicles that had same issue with no conclusions other than it may be the ECM. Are there any other relays that could be a problem? I do not have a schematic nor know which other, if any, relays to check. I already swapped the Fuel Pump Relay and Start Relay in the engine fuse box to see if any changes, it didn't seem t make a difference. Not sure what to do at this point. Any suggestions?
Last edited by Cjet; 07-20-18 at 01:21 AM.
07-11-18, 05:08 AM
#2
Lexus Champion
Help! My car cranks longer than it should to start. I recently changed the fuel pump and the fuel pressure regulator. Still having intermittent hard starting. I checked to see if there is voltage going to the pump when the start button is pushed in the first time (or the second time), when it should be priming for 2-3 seconds then turning off. Nope. No voltage, but when I put my foot on the brake and push the start button, I do get 11+ volts and you can hear the pump turn on. Eventually the car starts.
It seems to me the pump is working ok, but for some reason it is not getting a signal to prime (turn the pump on for 2 or 3 seconds, then off) when the start button is pressed with foot off the brake.
I have read other posts on the forum for other vehicles that had same issue with no conclusions other than it may be the ECM. Are there any other relays that could be a problem? I do not have a schematic nor know which other, if any, relays to check. I already swapped the Fuel Pump Relay and Start Relay in the engine fuse box to see if any changes, it didn't seem t make a difference. Not sure what to do at this point. Any suggestions?
It seems to me the pump is working ok, but for some reason it is not getting a signal to prime (turn the pump on for 2 or 3 seconds, then off) when the start button is pressed with foot off the brake.
I have read other posts on the forum for other vehicles that had same issue with no conclusions other than it may be the ECM. Are there any other relays that could be a problem? I do not have a schematic nor know which other, if any, relays to check. I already swapped the Fuel Pump Relay and Start Relay in the engine fuse box to see if any changes, it didn't seem t make a difference. Not sure what to do at this point. Any suggestions?
07-11-18, 11:41 AM
#3
Rookie
Thread Starter
Last edited by Cjet; 07-20-18 at 01:29 AM.
07-11-18, 01:46 PM
#4
Curious, why was the pump/regulator replaced?
also was there any dirt, debris, or sediment in tank? (usually from fuel)(if so look at the injectors)
check for dtcs (hard start/stall history codes)
also was there any dirt, debris, or sediment in tank? (usually from fuel)(if so look at the injectors)
check for dtcs (hard start/stall history codes)
07-20-18, 12:40 AM
#5
Rookie
Thread Starter
SOLVED!
I had bad info that the Lexus uses a 2-3 second prime during the start. It does not. There is no prime signal, the fuel is held in the fuel line up to the fuel rail by check valves in the fuel pump.
The problem I had was either the o rings on the fuel pump - to- fuel filter body were bad, or the new fuel filter body itself (not the screen that is on the bottom of the pump) was bad, allowing fuel to drain back into the tank, bypassing the check valve in the fuel pump. Nothing more frustrating than putting in brand new parts only to find them defective.
I had bad info that the Lexus uses a 2-3 second prime during the start. It does not. There is no prime signal, the fuel is held in the fuel line up to the fuel rail by check valves in the fuel pump.
The problem I had was either the o rings on the fuel pump - to- fuel filter body were bad, or the new fuel filter body itself (not the screen that is on the bottom of the pump) was bad, allowing fuel to drain back into the tank, bypassing the check valve in the fuel pump. Nothing more frustrating than putting in brand new parts only to find them defective.
Last edited by Cjet; 07-20-18 at 01:22 AM.
07-20-18, 01:23 AM
#6
Rookie
Thread Starter
07-20-18, 01:27 AM
#7
Rookie
Thread Starter
No codes.....it started with bad fuel trims, then eventually hard starting. No dirt in tank, injectors were taken out and cleaned. The cause was found to be either a bad O ring or Fuel filter assembly or both.
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03-05-20, 06:28 AM
#8
Driver School Candidate
Glad you were able to fix the problem. Did you personally do all the repair or did you take it to a dealership? I’m experiencing a similar problem with hard starts and my dealership is unable to diagnose the issue.
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