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lexpert, Lexus Master tech
Category: Lexus
Satisfied Customers: 2100
Experience:  Master Certified with lexus, 8 years experience with Lexus
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It cranks but will not fire, i gave it a shot of fuel and

Customer Question

it cranks but will not fire
JA: Have you checked the fuel supply? And are all the spark plugs working?
Customer: i gave it a shot of fuel and not fire so I figure it is spark. problem has come and gone and now seem here to stay
JA: What is the model/year of your Lexus?
Customer: 2000 RX300
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: yes, gave it fuel to see if fuel or spark and it seems to be spark
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 4 months ago.
Category: Lexus
Expert:  david craig replied 4 months ago.

Hi Im David, thanks for visiting the site. have you tested for spark with a spark tester?

Customer: replied 4 months ago.
no, just figured after i gave it a shot of fuel in the intake if it was fuel it would have fired
Expert:  david craig replied 4 months ago.

when you turn the key to the run position(not start) can you hear the fuel pump run for a few seconds?

Customer: replied 4 months ago.
no pump noise but dont think there ever was
Expert:  david craig replied 4 months ago.

when it was running there was.

Expert:  david craig replied 4 months ago.

do you have anyone to put their ear to the fuel door and listen?

Customer: replied 4 months ago.
never heard one
Expert:  david craig replied 4 months ago.

thats something i need to know to make sure the fuel pump is good.

Customer: replied 4 months ago.
tried but no noise, should it not have fires once I gave it some fuel
Expert:  david craig replied 4 months ago.

should have unless you have multiple issues.

Expert:  david craig replied 4 months ago.

if you cant hear it, the pump is not being energized.

Expert:  david craig replied 4 months ago.

if it didnt fire when you put fuel in the intake, then you are missing spark too.

Customer: replied 4 months ago.
ok now what?
Expert:  david craig replied 4 months ago.

do you have a multi meter?

Expert:  david craig replied 4 months ago.

do you have a spark tester?

Expert:  david craig replied 4 months ago.

ill be back in half an hour. gotta walk the pooch.

Customer: replied 4 months ago.
Expert:  david craig replied 4 months ago.

good. while im gone could you please check for spark?

Customer: replied 4 months ago.
I was told it was the ECU and picked up a used one but unless it is programed with the key it will not work
Customer: replied 4 months ago.
Sorry, need quality time with wife. Need to try again tomorrow.
Expert:  david craig replied 4 months ago.

ok. keep in touch

Customer: replied 4 months ago.
just check and there is no spark
Expert:  david craig replied 4 months ago.

ok. give us a starting point. when you turn the key to the on position(not start), does the check engine light come on?

Customer: replied 4 months ago.
the light is on
Expert:  david craig replied 4 months ago.

good. ok, when you try to start the car does the red security light go out?

Customer: replied 4 months ago.
Expert:  david craig replied 4 months ago.

ok. good. let me pull a print so we can electrically test some things.

Expert:  david craig replied 4 months ago.

ok lets check some fuses. mainly the ones on this print, but anyone that has to do with IGN/ECU/FUEL/START/AM/EFI

Expert:  david craig replied 4 months ago.
Customer: replied 4 months ago.
all the fuses are good
Expert:  david craig replied 4 months ago.

ok.

Customer: replied 4 months ago.
What is next?
Expert:  david craig replied 4 months ago.

if the fuses are good. and the engine isnt getting spark or fuel, Double check the 7.5 amp ign. fuse. if that is good. your computer is fried.

Customer: replied 4 months ago.
How do I change the computer since they are programed to the key? I have a different one and when I put it in the security light stays on when I crank it.
Expert:  david craig replied 4 months ago.

the computer and the immobilizer has to be replaced as a set.

Customer: replied 4 months ago.
Where is the Immobilizer?
Expert:  david craig replied 4 months ago.

its part of the ignition switch. its a small black box located inside of the steering column.

Customer: replied 4 months ago.
Can mine be reprogramed or just easier to get the immobilizer off the car I got the computer from.
Expert:  david craig replied 4 months ago.

probably easier and cheaper to get it off the donor

Customer: replied 4 months ago.
Then my keys will still work?
Expert:  david craig replied 4 months ago.

no, you'll need to new key made for the new ignition switch, the immobilizer and igniton switch come out as an assembly.

Expert:  david craig replied 4 months ago.

looks like this

Customer: replied 4 months ago.
I need the ignition switch and immobilizer off the donor car as well as the key if they have it correct?
Can I get my key programed to the immobilizer?
Expert:  david craig replied 4 months ago.

yes, you can have new keys cut/programmed

Expert:  david craig replied 4 months ago.

any update?

Customer: replied 4 months ago.
Changed everything security light does not flash so all should be good and it is still dead.
Now what?
Expert:  david craig replied 4 months ago.

the security light goes out when trying to start?

Customer: replied 4 months ago.
Expert:  david craig replied 4 months ago.

does the light flash when the key is out of the ignition and doors are shut?

Customer: replied 4 months ago.
the light flashes
Expert:  david craig replied 4 months ago.

ok, does the vehicle crank?

Customer: replied 4 months ago.
cranks fine
Expert:  david craig replied 4 months ago.

and still no fuel pump running for a few seconds when the key is on?

Customer: replied 4 months ago.
No fuel pump
Expert:  david craig replied 4 months ago.

ok, gain access to the fuel pump relay. pull it out. with your multimeter find B+ on the relay base. then turn the key on and find switched power in another slot of the relay base. there should be 2 slots that doesnt ever have power also. take a jumper wire and put one end into a slot with 12vdc and the other end into a slot with no volts. ,key on, see if the pump runs

Customer: replied 4 months ago.
Where is the fuel pump relay?
Customer: replied 4 months ago.
the pump runs
Expert:  david craig replied 4 months ago.

ok, now we need to know why it doesnt run with the key on.

Expert:  david craig replied 4 months ago.

i gotta go spend some time with my grand kids. ill be back on tonight

Customer: replied 4 months ago.
Did I get a bad box
Expert:  david craig replied 4 months ago.

i dont think so. do you have a noid light?

Customer: replied 4 months ago.
Noid light?
Expert:  david craig replied 4 months ago.

its a light that plugs into each injectors connector to see if it is getting pulse command from the computer.

Expert:  david craig replied 4 months ago.

harbor freight sells a set really cheap

Customer: replied 4 months ago.
Is that just like checking for spark
Customer: replied 4 months ago.
Going to get one now
Customer: replied 4 months ago.
Got a light and no power anywhere
Expert:  david craig replied 4 months ago.

no power to any of the injectors?

Customer: replied 4 months ago.
I just checked one.
Expert:  david craig replied 4 months ago.

you plugged it in to the connector and cranked the engine and no flashing?

Customer: replied 4 months ago.
that is correct
Expert:  david craig replied 4 months ago.

ok. gimme a sec, thanks

Expert:  david craig replied 4 months ago.

can you check for ground at the one injector that you tested please.

Customer: replied 4 months ago.
The black wire ?
Expert:  david craig replied 4 months ago.

heres a print

Customer: replied 4 months ago.
I will get back to you tomorrow AM
Expert:  david craig replied 4 months ago.

well the injector harness should run together and have a single gorund for all of them. ill talk to you tomorrow.

Customer: replied 4 months ago.
I checked two injectors that have a common blue and red wire and that is a working ground
Expert:  david craig replied 4 months ago.

ok. see what happens to that ground when the key is turned on

Customer: replied 4 months ago.
The ground goes away
Expert:  david craig replied 4 months ago.

ok. the ignition switch is sending power to the side of the injectors when turned on, which is what its supposed to do. next up is to do a continuity check of the fuel injector harness to the computer. check point to point. and also each wire to ground.

Customer: replied 4 months ago.
What am I looking for?
Am I checking the grounds?
Expert:  david craig replied 4 months ago.

no. you are checking the control wires from the pcm to the fuel injectors.

Expert:  david craig replied 4 months ago.

if they all are good on the continuity test, then the computer is bad.

Customer: replied 4 months ago.
Two computers same issue?
Expert:  david craig replied 4 months ago.

if the injector control wiring is good then yes. it cant be anything else. nothing stop the injectors from getting pulse except damaged wiring to the injectors a bad ignition switch or the computer. when you check continuity, make sure you check the grounds in the area of the computer for corrosion or looseness

Customer: replied 4 months ago.
After I ran the fuel pump it fired a couple of time. Will the computer be intermittent?
Expert:  david craig replied 4 months ago.

after you ran the fuel pump, there was enough residual fuel in the lines and rail for it to be able to fire a couple times. did you check the wiring continuity?

Customer: replied 4 months ago.
Why would it fire if we don't have spark?
I will be checking the wires shortly and get back to you?
Expert:  david craig replied 4 months ago.

we need to check for spark again. doesnt make sense

Expert:  david craig replied 4 months ago.

did you check for spark again?

Customer: replied 4 months ago.
This evening,
Expert:  david craig replied 4 months ago.

ok

Expert:  david craig replied 4 months ago.

any update?

Customer: replied 4 months ago.
I am still chasing wires, do you have a diagram of the injector where they go into the ECU?
Also, we still have the issue of no fuel pump running.
Is there a fuse I am missing or a fuse box issue?
I have borrowed a third computer and it still does the same so we can rule that out.
Expert:  david craig replied 4 months ago.

here again

Expert:  david craig replied 4 months ago.

is the red security light still go out when you try to start?

Customer: replied 4 months ago.
Ues
Customer: replied 4 months ago.
Expert:  david craig replied 4 months ago.

ok

Customer: replied 4 months ago.
wires are good. Any ideas where to go next? Still no spark and no fuel pump
Expert:  david craig replied 4 months ago.

let me think about this

Customer: replied 4 months ago.
any ideas?
Expert:  david craig replied 4 months ago.

it has to be a fuse or a connector that not connected. recheck every fuse in the vehicle. even it you dont think it has anything to do with the problems.

Customer: replied 4 months ago.
I have changed every fuse that I can find
Customer: replied 4 months ago.
Is there a relay i should be looking at?
Fuse box issue?
Expert:  david craig replied 4 months ago.

what about the efi relay? lets see if we're getting power to it

Customer: replied 4 months ago.
can you please send me the correct fuse box, the one you sent earlier does not match.
Expert:  david craig replied 4 months ago.

you have a 2000 rx 300 correct?

Customer: replied 4 months ago.
Customer: replied 4 months ago.
Sorry to be a pain, is there two relays for the EFI?

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