94 Viper starts, dies, but then starts and runs great

[Dr. Pepper]

Have a 94 RT10 with 15K miles. Ever since I've had it (about 6 years), when cold, it always cranks for about 7 to 8 seconds (I don't touch the gas pedal), then starts but immediately dies if I don't carefully feather the gas. If it dies, it will then start right up and run fine after that. I've heard this is a common Viper issue and I've never worried about it since the car runs great. A neighbor witnessed this the other day and was sure the throttle bodies needed cleaning??? Any ideas? thanks

 

[AviP]

I'd say check the plugs and/or wires first, throttle bodies next.

 

[MoparMap]

Almost sounds like a fuel pump issue, but I would think that would have consistent problems. Like the fuel rail is dry so it won't start right away until it builds pressure, but then runs out of the fuel in the rails until it catches up. Not sure how reasonable that is though.

As a side note, my car (gen 3) might be doing something similar, but I haven't tested it as thoroughly. It will crank for a few seconds and not fire, but when I let off the starter it will just barely catch and fire a few times and cough to life, then run fine. Have talked with some people about it and am planning to check my fuel pressure the next time I try to start it to see what that looks like since I just put a new pump module in. It doesn't do it consistently though that I can remember. I think it most typically does it after it has sat for a while after running, but not necessarily a dead cold start.

 

[kssssnake]

When you turn the key on you should hear the fuel pump. Let it run for a few seconds then start the car. If the problem goes away start looking down line. Haven't researched the fuel system, but assume it's the same as all cars of that age. Pressure regulator and bypass line. Sounds like the fuel lines are dry at start up. Would start by checking fuel pressure with a gauge. If the filter is plugged you would lose the top end. Mine acted like that when I first got it. The alarm connection was loose. Sometimes I would hit it with my toe and the engine would start then immediately die. Something else to check. BTW the alarm is disconnected now.

 

[MoparMap]

Don't know about the earlier cars, but I know the gen 3 at least was a returnless fuel system, so the "bypass" line was in the tank itself. Would still exhibit similar symptoms though. Just in case someone is looking for a return line and can't find one.

 

[Dr. Pepper]

thanks for the suggestions- I'll follow up on all of them.

 

[steve e]

Does that year Viper have a air idle control valve, if it does clean that and make sure its working.

 

[Magicboy2]

When I had this issue it was the security system. The security system in a Gen 1 isn't a hard cutoff, it lets it run for a few seconds and then shuts off. I had to replace the control module, and it was fine after that.

 

[Dr. Pepper]

Already disabled the security system some time ago- I'll try all of the above ideas- thanks

 

[InTheZoneAC]

When you turn the key on you should hear the fuel pump. Let it run for a few seconds then start the car. If the problem goes away start looking down line. Haven't researched the fuel system, but assume it's the same as all cars of that age. Pressure regulator and bypass line. Sounds like the fuel lines are dry at start up. Would start by checking fuel pressure with a gauge. If the filter is plugged you would lose the top end. Mine acted like that when I first got it. The alarm connection was loose. Sometimes I would hit it with my toe and the engine would start then immediately die. Something else to check. BTW the alarm is disconnected now.

definitely do this. I would wait for the pump to completely quit priming after the key is turned to on then try and start.

 

[ViperRed]

I had this problem big time, replaced the MAP sensor, it's much better now.
But it still happens when parked for a period of time.

 

[Dr. Pepper]

thanks again to all of you who have replied- I'll look at all of your suggestions...…….

 

[Superchargertoys]

Gen 1 and 2 Vipers (maybe other gens as well) have a one way check valve on the pressure side of the fuel pump... Over time this often fails, allowing fuel and pressure to bleed off quickly afyer initial prime when you first turn the ignition key When you turn the ignition switch to the on position, you first hear the fuel pump cycle on for a moment to prime the line. If the "check valve" is weak or failed it will allow the fuel to bleed back and removes fuel and pressure for initial fire.

To check if this is indeed your issue, you can try a simple test. After sitting for a min of a few hrs, (say first fire up for the day) do NOT start the car, instead simply cycle the ignition from off to run 5 times with a 3-4 second pause in between... On the 6th time, turn the ignition to engage the starter. If the car starts right away and runs fine from here on that day, unlike the sputter, feathering and stalling you typically see... it is entirely plausable your "Check Valve" needs to be replaced... What you have done is primed the line several times in a row, not allowing the failed check valve to bleed off fuel pressure for your initial start that day... Hope this helps, let us all know your reaults.

P.S. This can actually be a short term fix until you can replace the check valve.

 

[94ViperWC]

... it is entirely plausable your "Check Valve" needs to be replaced... What you have done is primed the line several times in a row, not allowing the failed check valve to bleed off fuel pressure for your initial start that day... Hope this helps, let us all know your reaults.

P.S. This can actually be a short term fix until you can replace the check valve.

Mine has the same problem (Gen 1), do you happen to know the part number for this check valve, and is this the fuel pressure reg. or something else? And any idea what kind of labor is required to replace? I heard it requires a dropped fuel tank...

 

[Tims 95]

I had this problem big time, replaced the MAP sensor, it's much better now.
But it still happens when parked for a period of time.

Which MAP sensor did you go with?

 

[ViperRed]

Which MAP sensor did you go with?

I was lucky to find one OEM from the dodge dealer.
Let me see if I can dig up the receipt and part number

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[steve e]

Just my 2 cents, I think your barking up the wrong tree, with a manifold absolute pressure sensor, you would get a code if it was bad. check fuel system for good pressure at start up-leaky check valve, check air idle control valve-sticking.

 

[Tims 95]

Just my 2 cents, I think your barking up the wrong tree, with a manifold absolute pressure sensor, you would get a code if it was bad. check fuel system for good pressure at start up-leaky check valve, check air idle control valve-sticking.

Can you expand on the "air idle control valve-sticking"?

 

[WickedSpeed]

How old is your battery?

1. If the battery cut off switch that was added to my car is used (for parking long term for example), then it will start, promptly die, then start up and run fine. As I understand it, this is because the ECU has to reset/relearn.

2. I had problems with my viper starting and idling over the weekend after fixing my sagging doors. Turns out all the opening and closing I did drained the battery, and the car would not start. Put it on a charger for an hour and it started, but would not idle. Did a drive - kept dying until about 15 minutes into the drive when it started to idle. Combination of relearning and getting enough of a electrical load to run the pump, injectors, etc properly. I put it on a trickle charger overnight and it's running/idling perfectly now. I did a bunch of research on other forums and facebook groups, and almost everybody said this was likely a problem with the battery. My battery is 4 years old and a lightweight type battery. I'm going to pick up a new normal battery this week most likely.

If your battery is old, get a fresh one, make sure it's fully charged, and I wouldn't be surprised if the problem went away.

-Wicked

 

[WeGoRTw]

@Dr. Pepper did you figure it out?

My Gen1 seems to be suffering the same. Cold starts take multiple 4-7 second attempts to start.

Reading the manual it surprising for a Fuel Injected engine it can be flooded and recommended to start with some to full wide open throttle.