Engine just stops intermittently, may or may not restart
 

Recently installed; Holley Sniper 550-510 by a mechanic. Has been running fine for two weeks. Recently; the engine will just turn off, then may or may not restart. I could try starting again in perhaps a few hours then the engine may start again. Fortunately; this problem has only occurred while idling in my garage and not on the road. The mechanic who installed this Holley Sniper has lost his business. I’ve been looking through the Holley Sniper PDF files for troubleshooting solutions but to no avail.
My other suspicion is a failing MSD Blaster SS coil. I’m currently on the third one which is about 3 years old. Within that time, the car has mostly sat in the garage.
Could anyone provide some basic troubleshooting suggestions?
Thank you,
Jim

How long after starting the engine does it shut down? Are there any odd signs that occur before it happens, such as any surging or chugging? When it dies does it sputter, or turn off as if you keyed the engine off?

My next set of questions would relate to how the system is configured. Is the system controlling engine timing, or is it handling fuel only?

If the system is handling fuel and timing, is the coil behind a ballast resistor, or powered by a resistance wire? I can't be 100% certain on the Sniper because I don't own one, but the FiTech's require a coil to be powered by a full 12+ volts. If a ballast resistor or resistance wire is used, once it heats up and drops voltage, the systems either can not control spark, or do so erratically.

If the system is not handling timing, but only fuel, I would test the coil and if it tests good, I would then reference the RPM signal to the Sniper. If the RPM signal drops, or you are experiencing electro-magnetic interference, the system may be shutting down. This could additionally be an issue with voltage to the Sniper dropping below about 10 volts. That would also cause a rapid shut down as if you keyed off.

If the car surges, stumbles or when it dies hiccups as if it's starving for fuel, I would then be looking at the fuel system as the likely culprit.

The first suspects are any crimp on electrical connectors that are in the engine compartment and subject to fast temperature changes.

A striped wire that can be seen to wiggle around in its crimp must be re- crimped down tight.
One thing that a have seen a lot even in aftermarket pre made wires that use crimps is that the wires insulation is in the crimp and the only actual electrical connection being made is purely by chance.

To narrow things down once the motor cuts out hook up your timing light , then if you crank the motor and it does not start, plus you see no flash of the timing light then you know you have no spark and it’s not a fuel system issue.

When the engine stalls--do you still have spark when the engine is cranked? If so, will it start if you supply fuel--a squirt of carb spray down the throttle body?

Do you have fuel pressure when the engine is cranked? Is this a system were you can see the injectors squirt?



If MSD was giving away "Blaster II" coils for free, I wouldn't walk across the street to get one. High-failure junk. You can test it with an ohmmeter, an ohmmeter can tell you if it's failed. The ohmmeter CAN NOT tell you that it's GOOD. You'll need a spark-tester and a spray-bottle of water for that. If a spark-tester calibrated for HEI ignitions will fire reliably when the coil is hot and the top surface is wet, it should be good.

I have an acquaintance here who had intermittent stalling problems with his Sniper and it turned out to be his fuel pump--it would just quit sometimes. How's your fuel system set up? What's going on with your fuel pressure right before it stalls and right after? If the car consistently restarted after it stalled, my first guess would be electrical interference. But it sounds like your car won't restart sometimes. This might happen if you accidentally flood the engine when trying to restart, so it may be electrical interference after all. The Sniper manual has several suggestions about how to route wires and so forth to avoid electrical interference gremlins. While taking care of this, you could also check the connections. After that, could verify the coil and ignition box.

I would not place a sniper and a blaster under my hood!

JMHO

Nice thing about the sniper and these EFI systems in general is you can datalog. A datalog may show some irregularities that stand out and give you a clue.

As others said I'd be curious of the type of fuel system, what fuel pressure is when this occurs, whether you're using timing control or just fuel.

Is there a fuel pump indicator light, or a fuel PSI gauge? If not then putting a little gas in the air path might reveal a start-up.

Or try the HEI ( waiting on the bench, to play for this reason), for some old time hockey action.

A while back a member here had issues similar to this with a bad O2 sensor harness. I think that thread is in the EFI section. That's one of the things that deterred me from a Holley system, all the connectors that both cost more the more you need, and add crimps done by someone else...

Good suggestions here (thanks to all). I had trouble following Holley tech support’s lingo, but I have a starting point; fuel and/or pump issues.

When the engine was running, the fuel gauge next to the throttle body read 100 PSI; should be 60 PSI according to Holley. When the ignition was in “ON” position (engine not running), fuel gauge read 15 PSI. Now; after numerous starts & stops, fuel gauge reads “zero” in the “ON” and “CRANK” position and of course will not start.

This entire EFI setup is new (as in weeks) including the gas tank and fuel pump (located in the tank). I could look for an obstruction in the fuel lines/filter, but if gauge reading zero while in CRANK or ON position, seems to me the fuel pump has failed.

Holley has a helpful flow sheet for fuel issues (https://documents.holley.com/199r11369.pdf).

As you said, fuel pressure should be 60. There's a fuel pressure regulator that's built into the Sniper, but from what I understand, they're prone to failure (or they had a run of bad regulators). You can replace it easy enough with a new unit from Holley, or just remove it and run an external regulator. But it sounds like you may also have a fuel pump issue. Check the wiring to the pump (power & ground). If the wiring looks good, you can see if the pump runs when you send power to it directly (disconnect the blue wire from the Sniper harness to the pump first). I'm not an expert, but this is what I would do based on my limited experience.

Is the gauge accurate? How do you know?

While not likely, a plugged fuel filter could cause lack of pressure downstream.

Don't drop the tank until you're sure the pump has adequate power. Lack of voltage will make for a "dead" pump. All it takes is a popped fuse, or a loose connection.

Yepp that was me, O2 wire harness burnt on the headder and grounded out , causing the the whole system to be inoperable.

Seeing as you had 100 PSI and now 0 psi i would suspect the pressure regulator as some debris could block it and now maybe hold it open bypassing everything.
If you open up the cover for the pressure regulator be prepared to put in a new o-ring as when i opened mine it had swelled and would no longer fit in it's groove.
Also handle the pressure regulator with care as too much pressure in the centre of it wil change the PSI set point of it.

The regulator housing is part of the return fuel line fitting on the TBI. when you undo the 4 screws holding it in, it will reveal a regulator like this: https://www.holley.com/products/ls_p...s/parts/12-878

Ooof, burnt wires on a header will do it :)

Is that automatic on the Holley, no O2, no workie? If say you have your fueling nailed down, can you lock out the O2 sensor? Or is there at least a limp mode? Makes me glad I can run without mine if I need to...

Don't need the 02 to run the Holley. In fact Id recommend once you have a tune nailed down I dummy down the compensation and learn limits and also keep a tune on file with all that disabled (no 02) just in case it fails you can run it open loop just fine as long as you have a good base fuel map.

I have limited my correction in closed loop and and learn. i leave the idle area a little more loose than full throttle and cruise, i think if you disable both closed loop and learn you disregard any O2 input, but in my case shorting out the burnt harness caused the ecu to not react to anything. Once i found the burnt wires and isolated them with vulc-tape and elctric tape + heatshrink. everything was working as normal again. Weird that it shut the whole system down with "no ecu found" message.

Correct, when you disable closed loop and learn it removes the 02 from the equation. It's always a good idea to keep a tune like that backed up on the SD card so that if your 02 every fails, you can simply use the hand held to load the (limp) tune. The engine should run fine if your base fuel table is dialed in.

How I do the regular tune with the base map dialed in is set learn to just 5%, that way if the 02 ever does fail it really doesn't corrupt the learn table, and I don't need it to learn more than that generally because my fuel table is within 1-3% anyway. I then let compensation make any necessary changes due to elevation.

On compensation limits, I keep WOT areas at 80 kpa and above at 20% to keep the engine safe for a few reasons. Constant elevation changes here I want the holley to correct WOT, that's the biggest reason I bought it.
The rest of the compensation limits I keep at 10% so it can correct on the fly.

I really don't like compensation limits too high in the light load, light throttle areas as it tends to over compensate and make big swings with AFR. Not sure what algorithm holley uses but seems to work fine at WOT where things happen much faster, but at light throttle tip in and generally during throttle transitions it tends to over compensate. For example if the AFR is just 2-3% off one way or the other, lets say rich for instance, and I'm only at 8% throttle, compensation tries to catch it and goes off the deep end subtracting 10-12% or something crazy, which causes a slight lean surge and then swings back the other way to fix that, and it's this constant big swing that really isn't necessary. Takes it a few seconds to settle down but will repeat the process any time you tip in the throttle.

So I found that if I limit compensation to 10% or less in those areas the problem goes away and the car runs much better. It really needs to be less aggressive in the light load areas and more aggressive at WOT, so that's why I set the limits that way.

Just an update.

The gas gauge needle is stuck on ¾ full. So previously, when the engine suddenly quit and would not start, it’s because the tank was empty. I added 3 gallons, started right up. So this puts to rest my post, #10.
As for the intermittent engine shutdown, I’ll continue to look over the suggestions here (and troubleshoot the gas gauge).

Does this Sniper have the ability to data log? The data logging is very helpful in diagnosing. I had a similar issue with random shutdowns and the data logs showed random noise influencing the ECU. The issue ended up being one of the spark plug wires had damage to the insulation. Swapped the wires out and never had an issue since.