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George H.
George H., ASE Certified Technician
Category: Mazda
Satisfied Customers: 18394
Experience:  15+Years
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I have a 1991 Mazda 2600i truck. It will start immediately

Customer Question

I have a 1991 Mazda 2600i truck . It will start immediately but send gas out a lot tailpipe while it's running .it seems the 1&3 injectors are flooding I have replaced them and fuel regulator and filter . Still same . I pull the plug wires off 1&3 and it runs the same . So I guess only running in 2&4 . Is it computer ?
Submitted: 4 months ago.
Category: Mazda
Expert:  George H. replied 4 months ago.

Hello I will help,

It probably is the computer failing. Most of them do. The injectors are fired in pairs so first thing to do is pull the computer mounted in front of the passenger door opening and open it for inspection. If you see any burning or a whitish substance on the circuit board near the can capacitors you need another computer.

let me know how I can help you with this

Thank you

Customer: replied 4 months ago.
I have done that don't see any sign of corrosion
Expert:  George H. replied 4 months ago.

Then it could still be the computer have you looked at the photos online of damaged ones?

Are you confident you know what to look for?

Customer: replied 4 months ago.
No not confident . Just looks ok. Even though I can drive around yard at a loss of power I don't think it will make it to a garage to put on a computer
Expert:  George H. replied 4 months ago.

The is no computer to put it on. All testing is done by visual inspection or point inspection with a voltmeter.

Take a look at this site for images

It is so common for the computer to fail you have to be absoutely sure the computer is clean before proceeding to pinpoint test.

Expert:  George H. replied 4 months ago.

Do you know anyone with a 2600i? Maybe you could borrow their computer for 10 minutes to check if the problem goes away?

Customer: replied 4 months ago.
No I can't think of any .the computer board looks clean to me . Are their any ground spots that are prone to going bad or coming loose for the 1&3 injectors not to be working ?
Expert:  George H. replied 4 months ago.

The power for the injectors comes from the fuse block through the large injector connector under the intake. The ground for the injectors is through the computer. If the ground wire to the computer were shorted to ground then the injectors would stay on all the time the key was on. Inside the computer the injectors are grounded through one of the transistors mounted to the side of the case. It is common for this type of transistor to short and ground all the time. Usually there are slight burn marks where the transistor is soldered to the circuit board or where the large connector is soldered to the board.

You can check if the injectors are shorted with a meter, same for the wire to the computer.

Customer: replied 4 months ago.
My son has a volt meter but doesn't know where to test ? Or how many volts it should have ?
Expert:  George H. replied 4 months ago.

Has any work been done or damage to the wiring? A visual inspection of the wiring would be the best place to start. You can only get to the #1 injector without removing the intake, the large connector near the back you can see the wiring running into from the injectors will be the place to check.

I can't walk you through all the testing and how to do it, that would be many hours work.

Customer: replied 4 months ago.
Since 1&3 are flooding all the time are they seperatlly grounded ? Are there seper ate grounds for each injector ?
Expert:  George H. replied 4 months ago.

No, as I posted above they are fired in pairs so one transistor runs the ground for each pair of injectors. 1 and 3 are a pair, 2 and 4 are the other pair.

Customer: replied 4 months ago.
Do you know which transistor runs 1&3 ? Or could give me like just the first couple places you would check for the 1&3 injectors . We have visually looked at the wires and inside the computer . But don't know where to start for the 1&3 .
Expert:  George H. replied 4 months ago.

I really think your issue is in the computer Maybe you could take it to a shop and have them take a look?

I am going to OPT OUT as this is much more work than I am willing to do here

Customer: replied 4 months ago.
No work has been done lately . I just started it up one day and this started .it is old but doesn't have many