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PT & WB (Twin Axle Pusher Unique Issues) If you have a unique issue with your PT or WB model coach and it can't be answered in one of the other forums here, then this is where you can list it....list your PT Parts here too.

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Old 05-09-2021
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jimbonich jimbonich is offline
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Default 93 8V92 Cranks But No Fuel

After reading some more recent threads I decided to try and resume troubleshooting why my engine suddenly stopped starting while diagnosing airing up problems some time ago.

Here's where I am now-

AT Switch is in correct position--engine won't crank in other position.

Front/Rear switch at rear is in correct position (actual key switch was removed years ago, but engine only cranks when front/rear switch is in Front position).

Both fuel filters remain completely full.
Generator has plenty of fuel and runs for hours
Coolant sensor was been wired around, plus earlier experience has been that engine goes into limp mode vs. cutting off fuel.

When front ignition key is turned to On position the following happens:

Check Engine light comes on and stays on

Do Not Shift indicator flashes constantly

Check Trans indicator stays on constantly--no blinking or codes

Neutral light illuminates

Green cruise control indicator usually comes on and stays on.

Engine cranks and cranks but no fuel. I haven't tried spraying anything into air cleaner to assist, but the engine started immediately and ran repeatedly when I was working on the air system, then abruptly just stopped getting fuel the next time I tried to restart. No fuel starving or skipping or trying to start or air in the fuel lines that I could detect.

After reading Jerry Rivera's thread I see several similarities to what his engine was doing with a malfunctioning rear/front switch. However, once I reset my AT switch to the correct position my engine cranks but gets zero fuel.

Again, it was like a switch was flipped--multiple lights come on and stay on, engine cranks but no fuel.
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'93 PT40WB
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(Previously Pair of Jacks)
Saint Petersburg, FL
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Old 05-09-2021
Alever Alever is offline
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Jim, if your check engine light comes on and stays on there is something wrong in the system. Did you do the code blink by pushing and holding the check engine light down? It takes a few minutes to do. It starts blinking the lower codes first and works its way up. It will then pause for a couple and start over. I have to use a piece of paper and count the blinks to keep myself from getting confused.
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Allen and Sara Eversman
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93 WLWB
Had 81 FC35
937-407-0079
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Old 05-09-2021
mose mose is offline
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All this is from my '91 8V92 DDECII, so should be similar...


If the 'stop' and 'check' and 'do not shift' lights don't go out after a few seconds, might be missing a power supply to the ECU. Many of the lights such as the 'cruise enable' get their +12V power from the key switch and they are toggled on/off by the ECU applying GND to the other side. So on initial key-on, many of the lights come on, then once the ECU is happy, it turns them off (check engine, stop engine, etc.). I believe the 'Check Trans' remains lit until the engine is running.

I'd start by checking a few of the ECU breakers and relays:

1) ECU diodes. Under breast plate. Terminal #2 on lower, center terminal strip should have +12V with key on.

2) Those diodes feed the ECU relay, which is K20 under breast plate. Can check that relay has +12V in and out on terminals 30 and 87.

3) Breakers that feed the engine ECU power. Mine are hidden on the inside of the left wall in the battery bay. Should be +12 on both sides of all 3.

4) unplug, clean and re-plug the connectors on the ECU on the top of the engine.

Check those first and go from there.

...mose
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Last edited by mose; 05-09-2021 at 04:08 PM. Reason: added #4
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Old 05-09-2021
mose mose is offline
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Here's where my ECU breakers are located. I think I've seen them over above the Racor as well.
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Old 05-09-2021
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Quote:
Originally Posted by mose View Post
Here's where my ECU breakers are located. I think I've seen them over above the Racor as well.
Wow--that's a huge amount of help. Will resume diagnosing in the cooler morning hours. What you're saying really makes sense, but my tiny BB blueprints and failing eyesight makes tracing the circuits very frustrating.

Thanks!
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'93 PT40WB
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Saint Petersburg, FL
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Old 05-09-2021
Alever Alever is offline
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Default DDEC 2 ECM Power Sources 93WB

Jim, Let me add a little to this. The power for the DDEC 2 ECM comes from three 20 amp circuit breakers located to slightly under and to the left of the Racor filter at the back of the bus. You can only see them with the side door open like when you go to change the Racor filter out. Not a very nice location for circuit breakers as all the road crud can get up there. I would take a test light and make sure all of them are passing voltage to the wires coming out of them. Try to get on the ring terminal that the wire is crimped too. The stud may read good but there may be enough build up between it and the wire to keep from passing any voltage. All three have to work to start and run with the computer. One goes to the key switch, bulk oil fill switch and the engine bay lights. The other two go directly to the DDEC ECM to operate it. I believe they are both needed to start the engine and are redundant for safety when the engine is running.
It's a good place to start.
Keep us posted.
Good luck too!
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Allen and Sara Eversman
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Had 81 FC35
937-407-0079

Last edited by Alever; 05-09-2021 at 05:06 PM. Reason: Added picture of circuit breaker location
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Old 05-09-2021
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Yep... great place to put circuit breakers! Would love to meet that engineer someday when he's real proud of his work

I'd been brainstorming with brother Jim about this for several months- but I am a non-DDEC owner. Have heard many comments over 17 years about good voltage being required for the DDEC to function, so this seems logical. I did not know where the power originated- but those circuit breakers would be suspect in my world.
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Old 05-09-2021
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If you ever have an extra hour or two just ask Shane about electronics and he will tell you that a 40 foot mechanical cable running to the back of the coach is the way to control your engine and related components!

I think Alan and Jerry have me on the right track--mine is acting like Jerry's did with a bad front/rear start switch--without complete power to the ECU lots of weird things light up. Since my engine cranks it makes total sense that one of the ECU fuses, power leads, circuit breakers, etc. is malfunctioning.

The fact that this is a reasonable and logical explanation worries me. A lot.

Stay tuned and thanks!
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'93 PT40WB
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Old 05-09-2021
mose mose is offline
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Quote:
Originally Posted by mose View Post
Here's where my ECU breakers are located. I think I've seen them over above the Racor as well.
That picture was embarrassing. So I relocated and replaced those breakers.
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Old 4 Weeks Ago
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Default DDEC 2 POWER SOURCES

DDEC 2 power sources come from two different insulated studs that get power from the engine batteries and through three 20amp circuit breakers at the rear of the bus.
The breakers do the following:
1st breaker (bottom in picture and is shown top on the BB electrical drawing) is the single one with one small wire on the input from the battery and three small wires on the output side that provide power to both front and rear ignition (start) key switches for the ignition and start control operation, the bulk oil fill and the engine bay lights.
2nd and 3rd breakers are powered from a single larger wire and tied together on the input side of the breaker. One powers the right bank injectors and one is for the left bank injectors.

You can have ECM power and the check engine light and warning lights will work. But the bus will crank but won't start because there is no power to the injectors (double breakers). The lights will stay lit because the ECM is telling you there is a problem.
If you have no check or warning lights and nothing else works when you turn the ignition switch it means there is no power getting to the switch or through the front rear toggle switch in the engine bay.

NOTE: Both front and rear key switches send the power for the ignition and start to the toggle switch at the rear of the bus. Out of the toggle switch one side power goes to the DDEC and the other side goes to the neutral safety switch then to the starter relay.
Also the AT switch on the dash needs to be in the proper position to start the bus. The ATEC is what controls the neutral start relay operation. If the AT switch is off, the ECM relay has no power so the ATEC transmission controler has no power and neutral safety relay will not close to complete the start circuit.

The ECU diodes and ECU relay is for the ATEC Transmission computer only. FYI
I will add to this as I find more in the future.
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Allen and Sara Eversman
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93 WLWB
Had 81 FC35
937-407-0079

Last edited by Alever; 4 Weeks Ago at 12:11 PM. Reason: More neutral start relay information
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