What does a 4.0L camshaft synchronizer control?

[RedNeckRanger]

I've got a 1994 Mazda B4000 (Ford Ranger) with a 4.0L OHV, and recently had to replace the sensor only (not the complete synchronizer assembly) due to a rough idle, misfire and DTC. I had to go with a used part because I couldn't afford a new or reman. unit and now my truck cranks but won't start. I have zero fuel pressure at the fuel rail and can press in the schraeder valve and not a drop of fuel comes out. I know that the synchronizer controls ignition timing and injector firing, but does it also control fuel pump operation? When I turn the key on I hear the sound that the fuel pump makes when it's normally priming but get no fuel when cranking. I can't seem to find the answer to this in my repair manuals or online. Thanks in advance.

 

[JoshT]

Seriously though, I assume that you have already verified that it does in fact have gas in it.

The synchronizer has nothing to do with the fuel pump. You say that the pump is running so the emergency disconnect isn't tripped and I'm thinking non-electrical issue. Even if you aren't getting fuel pressure check to see if you are getting fuel at the fuel rail. It could be that you have a leak between the pump and the sender line that it just dumping the fuel right back into the tank, or that somehow the pickup in the tank got blocked/clogged.

Basically my troubleshooting process would be.. Disconnect the feed line at the rail, place in suitable container, flip key to prime pump. If you are getting fuel but no pressure, I'd be questioning the fuel pressure regulator. If no fuel at rail repeat the process at the filter, and install a new filter if it hasn't been replaced recently. If there is fuel there, see if replacing the filter is getting fuel to the rail and if it pressurizes. If no fuel at the filter I'd be looking internal to the tank. Pull sending unit and check hoses and pump pickup.

 

[SenorNoob]

^Good advice.

 

[RedNeckRanger]

Thanks for the advice. I plan to verify tomorrow that my fuel gauge is accurate and that the tank isn't empty. I'll put some more in just so I know that there's some in there for sure. If that doesn't work then I'll work my way back from engine to tank until I find the answer.

 

[rhekman]

I've got a 1994 Mazda B4000 (Ford Ranger) with a 4.0L OHV, and recently had to replace the sensor only (not the complete synchronizer assembly) due to a rough idle, misfire and DTC. I had to go with a used part because I couldn't afford a new or reman. unit and now my truck cranks but won't start. I have zero fuel pressure at the fuel rail and can press in the schraeder valve and not a drop of fuel comes out. I know that the synchronizer controls ignition timing and injector firing, but does it also control fuel pump operation? When I turn the key on I hear the sound that the fuel pump makes when it's normally priming but get no fuel when cranking. I can't seem to find the answer to this in my repair manuals or online. Thanks in advance.

You are correct the cam synchronizer tells the ECU what phase the camshaft is in and then combined with the crank position sensor (CPS) to time injector firing to coincide with each cylinder's intake stroke (giving Sequential Fuel Injection). I have a previous post on testing the cam synchronizer and verifying its operation by barring the engine over while watching a multimeter. https://www.therangerstation.com/forums/index.php?threads/4-0-ohv-idle-issue.204131/#post-2014445

As far as I know, the cam position sensor should have no effect on the fuel pump and the presence of fuel at the pressure regulator or on the rail.
As others have mentioned, I'd start by making sure I have supply by working my way back to the tank step by step. Pressure regulator, then filter, then pump.

 

[SenorNoob]

I've heard that the 95-96ish trucks will run just fine without the cam synchronizer. The PCM just uses the older batch fire code.

 

[RedNeckRanger]

So I've done some investigating and have found that the fuel pump is no longer making the priming sound when the key is first turned on. I have added more fuel to the tank to verify that it isn't empty and that the fuel level sender is working. I have 12 volts present across the fuel pump fuse and at the fuel pump relay and hear the relay click when I first turn the key on as though it would be controlling the pump to prime the system. There is still no fuel present at the test port on the rail or at the high pressure line at the regulator. At this point I think I need to drop the tank and check that the pump wiring is intact and that 12 volts is present at the pump. I'll check for fuel pressure at the fuel filter inlet and outlet just in case, but it's looking like a fuel pump problem.

 

[SenorNoob]

It's usually easier to take the bed loose and reach the tank that way. Especially if it's full.

Just unplug the tail lights and unscrew the filler neck flange. Then the bed bolts and a jack.

Good luck whichever way you go.

 

[cai]

I've got a 1994 Mazda B4000 (Ford Ranger) with a 4.0L OHV, and recently had to replace the sensor only (not the complete synchronizer assembly) due to a rough idle, misfire and DTC. I had to go with a used part because I couldn't afford a new or reman. unit and now my truck cranks but won't start. I have zero fuel pressure at the fuel rail and can press in the schraeder valve and not a drop of fuel comes out. I know that the synchronizer controls ignition timing and injector firing, but does it also control fuel pump operation? When I turn the key on I hear the sound that the fuel pump makes when it's normally priming but get no fuel when cranking. I can't seem to find the answer to this in my repair manuals or online. Thanks in advance.

Clogged line or fuel filter under side of truck.

 

[Broosedamoose]

I second what @SenorNoob said! Dropping the tank is much more of a PITA IMO!