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Thread: Holley Sniper Ignition Timing

  1. #11

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    Hi Danny. Sorry to bother you again.
    I did the conversion from external to in-tank pump in my Cadillac. When I started up the 472 after this conversion, something strange happened.
    It backfired so violently that it took out my starter. Broke the starter drive house in three parts. But that's OK. Had a new one, so I just mounted that and
    everything seems OK. But when I started the engine again, it ran very strange at idle, or it only runs at idle. If I try to give it some more pedal, it stalls.
    And the idle is very rough. Do you think the backfire could have taken out my oxygen sensor? It's mounted approximately 6" from the right hand manifold flange?

  2. #12
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    Quote Originally Posted by Lars View Post
    But when I started the engine again, it ran very strange at idle, or it only runs at idle. If I try to give it some more pedal, it stalls.
    And the idle is very rough. Do you think the backfire could have taken out my oxygen sensor?
    I suppose it's possible, but I would check fuel pressure first, since you changed the fuel pump.

    It's mounted approximately 6" from the right hand manifold flange?
    Was this location working fine before?
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #13

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    Yes it was. The oxygen sensor has been in the same place since I installed the Sniper. And the Cadillac has been running well.
    I was fooling around with the timing a bit. Because I didn't understand how to setup ignition & timing with a stock point distributor.
    But with your good help, I was corrected & learned. So no I have stock timing setting and intake vacuum advance.
    The fuel pressure seems to be steady 50 psi when turning on ignition. What it is when I crank the engine, I don't know.
    Should probably get some one to look while I crank. There's no way this shows on the screen is it?
    Last edited by Lars; 05-29-2017 at 09:01 AM.

  4. #14
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    Quote Originally Posted by Lars View Post
    The fuel pressure seems to be steady 50 psi when turning on ignition.
    Was it always 50 psi? The Sniper is supposed to be 58.5 to 60 psi.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #15

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    OK. Is there anyway the display can indicate that the oxygen sensor is defective?

  6. #16
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    No: http://www.youtube.com/watch?v=s3R8whD3ZWg (Wideband O2 Sensor Test)
    Key-on/engine-off. Also, the sensor heater will time out, so you'll need to work fast.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  7. #17

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    The touchscreen can display what the fuel pressure is supposed to be. But Sniper EFI doesn't have a fuel pressure sensor so there's no way to display the actual fuel pressure. You should be able to run the fuel pump, and pressurize the fuel system without cranking or running the engine. In this post, Danny tells how to make a jumper relay: Yes, you can jump fuel pump relay terminals #30 & #87. You should see approximately 58.8 psi in your fuel system with just the fuel pump running. What is your new fuel pump? There have been some defective regulators in Snipers, and these regulators may not play well with big fuel pumps. If you don't have the correct fuel pressure without the engine running, there's a problem with your fuel system.

  8. #18
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    Quote Originally Posted by 351C Sniper View Post
    You should be able to run the fuel pump, and pressurize the fuel system without cranking or running the engine. In this post, Danny tells how to make a jumper relay: Yes, you can jump fuel pump relay terminals #30 & #87.
    Yes, check fuel pressure (LINK). You can use THIS and one of THESE fuel pressure gauges at the -6AN fuel feed line fitting.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  9. #19

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    Thanks for all your help guys. I have a Walbro pump in a Tanks Inc. PA4 kit. I also have a fuel pressure gauge. But it's in the engine compartment, under the air filter. Trying to keep my Cadillac's engine compartment as stock as possible. So I have to turn on the ignition and look at it closer. Will do that this evening. And I'll also read all the info and watch the videos. I'll come back with an update of what pressure I have. And will also test the oxygen sensor. Thanks again Danny & 351C.
    EDIT: Sorry, not turn on the ignition of course, to see the fuel pressure. I'll jump the relay as you wrote. Thanks.

  10. #20

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    Hi again Danny. I've done some testing. Not tested the oxygen sensor yet, but I shall do. But I tested the fuel pump. I jumped the fuel pump as you advised me to. And it gives, on my gauge, 60 PSI. More or less steady. It might have gone a little over too. But today too, it starts & idles very rough. But when I lightly try to throttle it stalls immediately. After shutting down I opened the the throttle wide open, and with a flash light I could see that there was a lot of gasoline in the intake. Seems to me it got way too much. Could it be the regulator failing? Should I disconnect the return line at the tank and see if it returns anything to the gas tank? Thanks again for all your help.

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