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Open Roads Forum  >  Class A Motorhomes

 > Winne-will not start

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DANDEAKINS

CHATTANOOGA

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Posted: 02/09/12 01:18pm Link  |  Print  |  Notify Moderator

Tks Guys, I didn't see the last two replies. Sorry.When i turn on the switch the fuel pump does run a few seconds and stops. turn switch off wait awhile back on and it repeats. I am going out now and break the fuel line coming in at the throttle body and see if any fuel is coming through. Tks again guys.

1995brave

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Posted: 02/09/12 01:29pm Link  |  Print  |  Notify Moderator

If you have fuel there and have changed the filter , next thing to try is pull the injectors and try starting to see if fuel is getting to the injectors. It could be the injectors could be bad(two at the same time, don't think so) try connecting a 12volt light to the injector wires and cranking, look for the light to light up( do it in the dark, easier to see).

DANDEAKINS

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Posted: 02/09/12 01:56pm Link  |  Print  |  Notify Moderator

Tks BRAVE, After breaking the inlet side of the fuel line at the throttle boby i am not getting fuel while turning over the engine ...But now here is the strange part... I can put 12 volts directly to the fuel pump wiring at the tank and fuel pump will run and thru all filters and to the throttle body. Again i am not getting any fuel thru injectors either way.

cdking1

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Posted: 02/09/12 02:33pm Link  |  Print  |  Notify Moderator

Hi, one more try, it sounds like you are not getting power to the computer. If I remember right the computer controls the voltage to the injectors, initially, it applies a voltage to operate the front one, and as the engine warms up it starts cutting/thinning the gas that the TBI squirts into the manifold, leaner and leaner until the oxygen senser stops it. So you need to reset your computer. I think you disconnect the battery for some period of time, 30 minutes comes to mind. with the ignition off reconnect it. Then try it again. this is a simple procedure that could fix the problem. Also you might check and see if there is a computer fuze. Also,the house batteries should have no function in the engine running, they are normally isolated to prevent the house from running the chassis battery down. charlie in texas


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DANDEAKINS

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Posted: 02/09/12 02:52pm Link  |  Print  |  Notify Moderator

O.K. GUYS< Here i go, going out to disconnect the battery and leave it that way over nite. Anybody know where the fuel relay might be? I'll have a code reader tomorrow. Again thanks

enblethen

Moses Lake, WA

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Posted: 02/09/12 03:44pm Link  |  Print  |  Notify Moderator

Fuel pump relay on mine is hanging above the fuse panel under the dash.
Another fuse is the ECM?BAT, it should be hot all the time. feeds through the oil pressure switch and feeds contacts on the fuel pump relay .
There is or should be another fuse marked "Fuel Pump" that also powers the fuel pump.
I still beleive it is an electrical issue that is causing loss of fuel to engine.


Bud
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1995brave

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Posted: 02/09/12 03:56pm Link  |  Print  |  Notify Moderator

DANDEAKINS, found my Chiltons manual. The number is 28642 and it is for General Motors Full-Size Vans 1987-97 It includes the P series.If you can find it you want to look on page 6-76. The fuel injectors get their power from the ECM-1 fuse 10 amp. It is hot in Run, bulb test, and start. It is a red wire going to the injectorstied to the red and white injector wires. A ground from the computer fires them.

Edit: wrong page, fuse designation, and color of wire.

Daveinet

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Posted: 02/09/12 04:41pm Link  |  Print  |  Notify Moderator

cdking1 wrote:

Hi, one more try, it sounds like you are not getting power to the computer. If I remember right the computer controls the voltage to the injectors, initially, it applies a voltage to operate the front one, and as the engine warms up it starts cutting/thinning the gas that the TBI squirts into the manifold, leaner and leaner until the oxygen senser stops it. So you need to reset your computer. I think you disconnect the battery for some period of time, 30 minutes comes to mind. with the ignition off reconnect it. Then try it again. this is a simple procedure that could fix the problem. Also you might check and see if there is a computer fuze. Also,the house batteries should have no function in the engine running, they are normally isolated to prevent the house from running the chassis battery down. charlie in texas
Are you sure? I have spent many many hours studying the '95 GM ECM, I have never heard of seen anything like that. Some TBI systems have a cold start additional injector, but not the '93 - 95' 747 ECM. Cold start is blipped to put fuel in the engine, and then as it cranks, it pulse the injectors to start. Once the engine starts, it runs in open loop until it warms up. Fuel mixture for open loop is primarily determined by MAP sensor and RPM VS temp. As the engine warms up, the fuel table is screwed, until the O2 sensor is warm enough to read accurately, and then it goes into closed loop. Fuel is still determined by the MAP vs RPM table, and then fudged based on O2 readings. Either way, this will have no bearing on the engine starting. Besides, the initial pulse of the injectors when the key is first turned on, will put enough fuel in it to fire the engine momentarily, even if it never fires the injectors after that.

The fuel pump is probably working, so look farther down the line. Either clogs somewhere, or I have another one for you. Smack each injector with the back side of a screw driver. I have seen the injectors stick, which of course it won't run after that - hence the smacking. I highly doubt the code reader will tell you anything. The fact that it runs says that the ECM thinks everything is OK. I can't think of any instance where the ECM would spark, but attempt to run the injectors. You can take a light bulb to the injector wire as suggested. That should give you warm fuzzies that the injectors are being told to fire. You should be able to do all your testing just by turning the key, as when you turn the ignition on, it fires the injectors momentarily to spill a little extra fuel in the manifold to prepare the engine to start. Mine, I can actually hear the injectors click when I turn the key. If you want, put a small plastic hose with one end touching the injector, and the other end to your ear. You should be able to hear the click.


Dave

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enblethen

Moses Lake, WA

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Posted: 02/09/12 05:02pm Link  |  Print  |  Notify Moderator

I am not sure that we know the fuel pump is working through the factory wiring. OP applied power to the pump directly.
The fuel pump fuse supplying power trhough the oil pressure sensor is the one I would look at. The ornage wire to the oil pressure sensor should have continuous 12 volts from the fuel pump fuse. Then by my wiring diagram it leaves the oil pressure sensor via a gray wire to go to pump.
OP: did you open both lines at the TBI? one should not have fuel under pressure. The other should. The side with the linkage should have fuel under pressure.

DANDEAKINS

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Posted: 02/09/12 05:59pm Link  |  Print  |  Notify Moderator

MAN O MAN--Thanks for the response. I figured i would look at the web site one more time before lights out. Yea, the fuel line (pressure side) was the one i broke loose. I believe y'all might be on the right track and getting closer. As i said before, Bye unplugging the fuel pump wires at the rear over the tank and 12 volts applied to the pump side, the pump will run and squirt fuel out the fuel line at the throttle body.It will not plugged up and using the starting switch. I will buy a circuit checker tomorrow to read the fuse connections and any other that i can see. Also all the other things Ya'll suggested. THANKS GUYS VERY MUCH !!!!

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