20 replies to this topic

[john mueller]

Okay, I've done this exact job like six times times...

1.6 long nose, R&R the head (I do this every 2yrs), change the water pump, timing belt & install cleaned/matched injectors. I've checked all the below three times:

• Cams had the locating pins at 12 o'clock when the cam gears were reinstalled
• Belt looks to be perfectly timed ("I" &"E" are at 12 o'clock positions)
• Crank was at TDC when belt was installed
• Cam Angel Sensor was checked, looks to be correct.
• All electrical connections have been restored
• All three ground wires are intact
• Crank bolt has installed & torqued
• Motor cranks freely
• There is no water in the cooling system
• Crank pulley/harm-balance & alt belt have not been installed

What is happening:

• Fuel pressure holds at 35lbs unless the motor tries to start then it drops to 10lbs.
• Then I use a jumper to run the fuel pump there is noise at the fuel rail that sounds like a 'air leak', but there is no fuel leak and when I pull the jumper (turn FP off) the pressure holds.
• I had one really solid/loud backfire

Please suggest anything... I'm in the trees & cant see anything clear right now.

[Will Schrader]

Is it possible that you have the fuel lines reversed?

[Bench Racer]

Haynes Repair Manual has a description which works well that I've used two times.

[john mueller]

Is it possible that you have the fuel lines reversed?

It is, but they are not...

[Rob Burgoon]

Spark plug wires in correct order?

[Austin Robison]

Spark plug wires in correct order?

And are firing?

[DES4]

I'd try using a starter fluid (or carb cleaner/brake clean) to see if it'll fire. That'll confirm whether you have a fuel delivery problem or not. Checking for spark would be next if it doesn't...

A lot of possibilities here without confirming first where the base problem lies.

[john mueller]

Spark plug wires in correct order?

And are firing?

Yep & yep.

My gut says it's a fuel issue, I'm going to replace the fuel rail today and see what happens.

[Dave Lewis]

Don't go to the Haynes religously for your car, that bird cage liner is almost all 1.8. 1and4 wires go to the drivers side coil, 2 and 3 to the other.

[Bench Racer]

Don't go to the Haynes religously for your car, that bird cage liner is almost all 1.8.

Agree

I also have the FSM, I compare both , but I find some things easier to follow in the Haynes.

[DES4]

If you had it miswired, you'd have popping/backfires while cranking (assuming good spark and plenty of fuel). The drop in pressure while cranking implies that delivery volume is low... faulty pump or pump supply voltage/ground (check using pump ground at the pump; do voltage drop checks while duplicating the problem) or even a dry fuel pickup (low fuel level?)...

I'm guessing all was well before the engine was torn down...?

Seriously, though, spray a starter fluid in the intake while cranking to ensure it is fuel delivery. If you've got something like a power supply/ground issue that is affecting the ECM or ancillaries, it can create the illusion of a fuel or spark problem, and you'll chase your tail.

[davecarama]

There is a plug under the dash under the steering wheel area that I usually pull when I start the car to depressurize the fuel... is that pulled?

Do you have a new fuel filter? I have purchased some in the past that were bad (100% clogged).

Did you do anything else when you redid all of this stuff?

[KentCarter]

The fuel pump switch in the AFM. The big backfire may have knocked the vane back far enough to displace that switch. It will make fuel pressure during the priming phase, but the pump won't run unless that switch detects airflow.

[john mueller]

If you had it miswired, you'd have popping/backfires while cranking (assuming good spark and plenty of fuel). The drop in pressure while cranking implies that delivery volume is low... faulty pump or pump supply voltage/ground (check using pump ground at the pump; do voltage drop checks while duplicating the problem) or even a dry fuel pickup (low fuel level?)...

I'm guessing all was well before the engine was torn down...?

Seriously, though, spray a starter fluid in the intake while cranking to ensure it is fuel delivery. If you've got something like a power supply/ground issue that is affecting the ECM or ancillaries, it can create the illusion of a fuel or spark problem, and you'll chase your tail.

Yeah, I'm beginning to think it's a fuel issue but if it's being masked by an electrical supply/ground problem I'm done and will have to take it so someone ti look at... That kind of stuff is waaay outside my comfort zone unless I have step-by-step instructions of what & how to do it.

However I did try a few things: I replaced my 5X Fuel Pressure Regulator with my OEM spare, tried to fire but I still got the same result (no start) but with a LARGER pressure drop than before. So I put the jumper in like we all do when draining the tank, it fired but wouldn't stay running.

I know the original fuel filter was changed 18mos ago with a MazdaSpeed filter, I don't recall changing the fuel pump at that time. I may just change it anyway since I think I have one in the spares bin.

The fuel pump switch in the AFM. The big backfire may have knocked the vane back far enough to displace that switch. It will make fuel pressure during the priming phase, but the pump won't run unless that switch detects airflow.

Interesting, I'll check the position of the vane. Good suggestion, never knew this.

I have an in-line FP gauge that is on the fuel supply line so I can easily check to see if the pump is 'priming'. Anyone have a procedure or know what to look for?

[KentCarter]

When you turn the key on, the pump runs for a few seconds and then stops. You should see decent pressure in the line once it stops and it should hold pretty steady. When you crank the engine, the ECU looks for a signal from the little leaf switch in the AFM that the flap has moved (air is moving), it then restarts the pump. If it doesn't run, pressure will fall, of course.

[DES4]

Yeah, I'm beginning to think it's a fuel issue but if it's being masked by an electrical supply/ground problem I'm done and will have to take it so someone ti look at... That kind of stuff is waaay outside my comfort zone unless I have step-by-step instructions of what & how to do it...

If it is electrical, these cars are pretty simple and I can talk you through it; electrical problems are generally easy to solve, especially on these cars.

A good part of how I earn my living is electrical (I work on new cars that are far more complex than what we're dealing with here). PM me if you care to deal with it..

[john mueller]

When you turn the key on, the pump runs for a few seconds and then stops. You should see decent pressure in the line once it stops and it should hold pretty steady. When you crank the engine, the ECU looks for a signal from the little leaf switch in the AFM that the flap has moved (air is moving), it then restarts the pump. If it doesn't run, pressure will fall, of course.

Neat. I'll swap in another AFM if it doesn't prime and check again. If it doesn't prime either time then I feel it's safe to assume I have a pump (or pump circuit) issue.

If it is electrical, these cars are pretty simple and I can talk you through it; electrical problems are generally easy to solve, especially on these cars.

A good part of how I earn my living is electrical (I work on new cars that are far more complex than what we're dealing with here). PM me if you care to deal with it..

Thanks dude! I'll check the AFM and if it warrants a pump change I'll do that before I PM you for a chat. I checked, the pump has not been changed, so it's the original one from 1921 (yes, my 1.6's is that old)

[Glenn]

Neat. I'll swap in another AFM if it doesn't prime and check again. If it doesn't prime either time then I feel it's safe to assume I have a pump (or pump circuit) issue.



Thanks dude! I'll check the AFM and if it warrants a pump change I'll do that before I PM you for a chat. I checked, the pump has not been changed, so it's the original one from 1921 (yes, my 1.6's is that old)

You can also run a hot wire directly to the pump....temp of course....to see if the pump runs and pumps. Have you looked at the screen on the bottom of the fuel pump? Had MANY so clogged the pump would not work properly.

[john mueller]

You can also run a hot wire directly to the pump....temp of course....to see if the pump runs and pumps. Have you looked at the screen on the bottom of the fuel pump? Had MANY so clogged the pump would not work properly.

I built a fancy package shelf in my car, got it powder coated and everything. It looks nice but may require me to remove the hardtop to access the pump to inspect & test it. Next time I'll include a removable panel to make this kind of work easier. Hooray for my fantastic fabrication skills fail.

[Glenn]

I built a fancy package shelf in my car, got it powder coated and everything. It looks nice but may require me to remove the hardtop to access the pump to inspect & test it. Next time I'll include a removable panel to make this kind of work easier. Hooray for my fantastic fabrication skills fail.

Or loose a few pounds and just climb inside LOL Really only take 10 mins and DO NOT DROP THE LITTLE FRIGGIN SCREWS!!!!!!!