Zex problem

[Pat]

This is an info thread for Zex equipped Marauders.

A few weeks ago my Zex system, when activated by the TPS and Traction Window device, caused the car's engine to dramatically stumble. Zex off = Good. Zex on = jerky, stumbling engine.

I queried the Zex company and they responded within a few days with technical help. They are having me run through some diagnostic routines to isolate the problem.

I did find out one new thing, the nitrous input fitting on the NMU (purple box) is actually a very fine micron filter. If you need to check it for operation just blow through it. You cannot see through it so don't think it's clogged and stick a sharp instrument through it. This tidbit is not in the instruction/installation pamphlet.

I think the arming switch is my problem. It seems to be erratic, sometimes the NMU powers up and sometimes it doesn't. The Window switch powers up even before the arming switch is fully set to the on position. This may indicate an internal disruption.

I'll be changing the switch next week.

If you have not programmed your NMU you should. The procedures are in the pamphlet. Right now my solenoid check is failing, instead of one click at WOT the solenoids cycle rapidly like a machine gun.

Stay tuned for episode two - replacing the arming switch.

Regards,

Pat

[fairlane347]

I have Zex but not the window switch. I would think maybe it the switch. I have had no prblems yet. Good luck. BTW have you run your car with it? What did you run? I enjoy mine.

[Pat]

Yes I have, with just the Zex basic system, 100 shot, I was in the low 13's.

Never did as well on the strip with the S/C and nitrous, 50 shot. Needed traction help (wider wheels, drag radials, control arms).

But I did fine on the street with just the S/C.

Don't use the nitrous on the street, too small a town with too big a police force.

Glad that you enjoy yours.

Pat

[Pat]

OK, we got the new (20 amp) arming switch installed. (James79stang did most of the work)

The system now arms consistently and the solenoids click only once, not the staccato like before.

We will hot check it tomorrow on my private drag strip. Yea, the one that's not under water. We have had a lot of flooding as of late.

More later,

Regards,

[-Matt-]

great to hear that Pat, when do i get a ride in her?

[Pat]

Well, the new arming switch worked OK but it did not fix my problem. ZEX off=engine good. ZEX on=engine stumbles badly.

The ZEX tech asked me to test the system by monitoring the input to the nozzles.

So with the gasoline line disconnected at the nozzle and routed to a sealed container
and the nitrous gas line held by a willing co-worker with a stand-off tool we activated the system. Just turn on the ignition but do not start the engine, arm the system and depress the accelerator pedal to the floor (simulating WOT). and one should observe a huge stream of nitrous gas being vented into the atmosphere. So the nitrous gas side of my NMU is good, now to test the gasoline side.

The gasoline side was dead. No steam from the NMU to the nozzle. We then disconnected the input side and tested for gasoline stream. That was good. Plenty of pressure and volume from the fuel rail. Fuel was caught in a catch can.

A call to Parker Industries to obtain a replacement valve revealed that they only sell these valves to ZEX (Comp Cams) in a proprietary contract.

Contact with the tech at ZEX was productive. He will look at their stock of returned NMU's and see if a good fuel side solenoid is available for resell and/or sell me a reman'd NMU.

Whatever happens, My system will be running in due time.

Regards.

PS: I had the NMU completely disassembled, including the solenoids. Nothing magic in there or things that go "Boing".
The solenoids althought they look alike are very different internally. Orifice machining and pressure rating are big differences.
Howver, one can only partially disassemble the solenoid. Regardless, if it's bad you have to replace the whole thing anyway.
Both the fittings to the intake side of the NMU are filters and you should be able to blow thru them.

[RacerX]

Eek! So you were running lean! I thought you had an A/F lean shutoff w/wideband? Or is that someone else on here? Hope it's ok.

[Mr. Man]

Pat if you don't know about Zex at your age I think there is little we can do to help:P

[Pat]

Interestingly I thought the system had to sense both fuel and nitrous to operate.

Apparently this isn't so. The electronics only open the fuel and nitrous solenoids together when the WOT signal is detected. If one or both of the solenoids fail then the system will squirt nitrous oxide or fuel into the intake. You don't know which.
After taking the unit apart I find no flow sensors, just solenoid coil activation wires.

I'm pretty sure the stumbling engine was a result of the spark being blown out and not detonation. I've run it with this condition for less than thirty seconds on at least 8 times troubleshooting this system. The engine seems fine.

For some reason I thought it was the nitrous gas that was inhibited. And that the car was running pig rich with the extra fuel. The reverse was true. Whew........I'm lucky.

Pat

[justbob]

Pat, I only hope that when i'm 70 I'll be complaining about my nitrous armed, super charged car! Your awesome man!

[RacerX]

Can spaying just N2O cause blowout? You're aren't adding any PSI to the charge before ignition, just more oxygen per square inch. By the time it's ignited, I wouldn't think that would be an issue unless you had a multispark ignition system. Anyhoo, you ARE lucky! That could've been a liquid metal mess!