1995 Chevy G20 Van Wont Idle

Propane, Butane, LPG, GPL, C3H8, C4H10
Wopper
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Location: Delta BC Canada

Re: 1995 Chevy G20 Van Wont Idle

Post by Wopper »

OK, your pic the nipple below the hump, it has a slot across the top, is this what I connect vac for solenoid to?
Wopper !

C3H8
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Re: 1995 Chevy G20 Van Wont Idle

Post by C3H8 »

That's correct. On the underside of the mixer there will be a screw in the opening that leads to that hump. I am not sure of the words on the edge of the casting on the underside closed the hump but it may say EC1 instead of casting. Keep in mind that I still think the location you are currently using is acceptable but to be 100% sure you can change to this location. I still think your solenoid valve is the problem. To be sure you can remove the hose at the regulator vent and if the hesitation goes away the solenoid is the likely culprit.

If you have the mixer off for any reason check that the three screws that are in the deep recessed holes are tight. These are also the studs that come through the mixer to hold down the air cleaner plate. It is very common to have these loosen over time as the air filter is changed. The nuts used were self locking nuts and could eventually cause the screws to back out as the nuts were tightened. This would create a vacuum leak at the mixer diaphragm.

C3H8
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Re: 1995 Chevy G20 Van Wont Idle

Post by C3H8 »

Correction. I meant to say it may have the letters EC1 along the rim instead of VAC, not "casting".

Wopper
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Location: Delta BC Canada

Re: 1995 Chevy G20 Van Wont Idle

Post by Wopper »

Could not sleep this morning, thinking about this silly thing... :x So I got up early, swapped the vac line to your location, plugged the other spot I was connected to.
Fired up, drove to work ( Got here 45 minutes early !!! :mrgreen: ) , Again, good until warm, then again rough ( not quite as bad ) off idle, definately rich condition, you can smell rich fuel burning. :cry:
I will connect Voltage to solenoid for the drive home!! ( not Dark out) and see what I am getting..... :P
Wopper !

Wopper
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Joined: Tue Nov 12, 2013 8:59 pm
Location: Delta BC Canada

Re: 1995 Chevy G20 Van Wont Idle

Post by Wopper »

OK, on the way home, I connected the solenoid to voltmeter, when COLD, Voltage is being controlled under normal throttle settings between 2-8 volts. 8)

WOT was doing 15 volts….. :?

After warmed up, the rough stumble was giving 0 volt readings, accelerate slightly more, and voltage returns to 2-8 volt range. :x :x

Disconnected vac line from top of regulator, minor improvement in rough off idle acceleration, getting 12- 15 volts continuously. :x :x

Going to remove mixer again and look for the markings at the port you mentioned. :cry: :cry:

Hmmmm…….. :evil: :evil: :evil: :evil:
Attachments
Vacuum line connected under mixer top
Vacuum line connected under mixer top
Vacuum line connected under mixer top.
Vacuum line connected under mixer top.
Wopper !

C3H8
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Location: Winnipeg, Canada

Re: 1995 Chevy G20 Van Wont Idle

Post by C3H8 »

No need to remove the mixer. I can see your in the correct port. The voltages sound relatively correct. The basic operation of the 5920 and voltage reaction is as follows.

2-8 volts cold. Correct. This is a programmed voltage for the first 20 to 30 seconds of operation
Varying voltage at warm idle. Correct. the mixtures are in prescribed limit.

0 volts during acceleration. OK. The 5920 has commanded the solenoid to allow full venting to the reg so the diaphragm can move freely to supply fuel to support acceleration. This is a feed forward function programmed into the 5920 as it monitors the TPS. It sees the throttle opening and shuts off the solenoid.

Varying voltage at cruise conditions. Correct. The 5920 is in the feedback mode monitoring the oxygen sensor and controlling the mixtures as programmed.

Battery voltage or 15 volts at WOT. Correct. The 5920 is seeing very rich mixtures and doing it's best to pull the diaphragm by sending maximum vacuum and trying to lean out the mixtures. In this case it sounds like the power valve might even be slightly rich for the conditions.

Your fuel system is operating normally based on the data you have reported.

Back to basics. Quit blaming the propane system for now. The hesitation, miss, rough idle, heavy fuel consumption might be due to an ignition problem. Recheck the ignition, plugs, distributor cap, wires, rotor. Compression test numbers? Also look for vacuum leaks. Lastly check that solenoid that feeds vacuum to the EGR if you haven't done that yet.

Wopper
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Location: Delta BC Canada

Re: 1995 Chevy G20 Van Wont Idle

Post by Wopper »

OK;
Brand new plugs, wires, cap and rotor within the last month or less than 1000 k

Have not done compression test, but new head gaskets, ( thats what started this whole deal ) had the heads resurfaced to ensure good sealing surfaces.

What to check on solenoid feeding to EGR??
Wopper !

Wopper
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Location: Delta BC Canada

Re: 1995 Chevy G20 Van Wont Idle

Post by Wopper »

Thanks for all the help by the way, much appreciated!!! :D :D :D
Wopper !

C3H8
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Re: 1995 Chevy G20 Van Wont Idle

Post by C3H8 »

Your welcome on the assistance. Just hope we can find the problem.

First off the EGR. Just disconnect the vacuum hose attached to the EGR while it is idling rough and hold your finger over the hose. Does the engine smooth out? Do you feel any vacuum on the hose? There is normally no vacuum on this hose at idle. If there is any vacuum there at idle it could open the EGR a little and would account for the rough idle and hesitation.

Second. Saw all the new wires in the pics. looks good but looks can fool. Possibility of a cracked or bad plug. Also a possibility of a poorly sealing valve on one of the cylinders. I know this engine is a b**ch to work on getting at the plugs but at this time you need to know whether you have a bad valve. Do a compression test or leak down test.

Lastly, timing. What is the timing set at? Is it advancing properly off idle?

Forgot. One other question. Is it a heated oxygen sensor or is it a single wire oxygen sensor? Strangely enough some mid 90's vans came with an unheated O2 sensor. How old is the sensor?

Wopper
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Location: Delta BC Canada

Re: 1995 Chevy G20 Van Wont Idle

Post by Wopper »

Well, took it in to shop today to have it looked at, was getting beyond my level of patience…. and time limit.

So, they found new EGR was over sensitive and causing the hesitation, also, O2 sensor was not getting enough voltage output, so had to replace it ( Heated O2 sensor )
Also, a couple of wiring issues, one broken wire in the loom feeding the 5920, and a plug connection that was not properly connected.

O2 sensor disconnected now ( probably not going to connect it at this time ) and fuel levels and timing all rechecked, it is running very nicely now!

So, from your diagnosis, the last few things you suggested were right on, so thanks for your help!! :D
Wopper !

C3H8
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Re: 1995 Chevy G20 Van Wont Idle

Post by C3H8 »

Glad to hear things are looking up. Not sure if your going to like my next statements though.

You said the O2 sensor is disconnected. I'm presuming you mean from the 5920. That's OK except for two things.

If the 5920 does not see the mixtures change, which it won't if the O2 is disconnected it will abort all the other functions it performs except for keeping it on propane. The timing advance and knock diagnostic test, EGR diagnostic monitoring, O2 correction and feedback solenoid will normally be shut off if mixture monitoring is disconnected. Your check engine light will turn on and Aircare will fail a vehicle for a check engine light.

The other issue is the gas valve in the mixer should have been a rich gas valve to take advantage of the feedback system built into the 5920. This means the mixtures will be consistently rich unless the valve has been changed back to the standard gas valve. Emissions and economy will be poor unless the gas valve was changed. The economy will be OK if the gas valve was restored to the standard valve but the vehicle will likely fail the Nox test every time.

I'm curious as to why you chose this strategy. Did the engine still run poorly after the repairs with the O2 connected?

Wopper
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Location: Delta BC Canada

Re: 1995 Chevy G20 Van Wont Idle

Post by Wopper »

My mistake, Not O2 Sensor, EGR Disconnected….Sorry!
Wopper !

JrsPropaneParts
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Joined: Wed Nov 27, 2013 3:17 pm

Re: 1995 Chevy G20 Van Wont Idle

Post by JrsPropaneParts »

I skimmed through the previous posts so sorry if anything was repeated but be weary about taking an alternative fuel vehicle to just any shop most mechanics are unfamiliar with the systems dont understand them and just start changing parts.

I seen someone mentioned about the vacuum leaks with the head gaskets this is a very true statement your air to fuel ratio would change completely after fixing all your vacuum leaks.

Another question would be is were you experiencing back fires when the engine was having problems ? or did your engine over heat repeatedly or get very hot ? This can cause cracks in your mixer and would also through off your air to fuel ratio. Depending on what temps your engine got to and how often you might have cooked your gaskets inside the mixer.

When was the last time your propane system was checked / maintained. gaskets replaced ? its very important that your air valves in your mixer are clean and are able to move freely I am wondering if your engine was over heating it might have cooked the gasket stiffening it up not allowing it to move properly

How much horse power roughly do you think you have on that engine ?

let me know what ya can on this and I will assist you further with your system. I think your problem might be simpler then ya think you just need to talk with the rite person to get the rite answer on the LPG systems. Thanks I look forward to your reply

JR

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