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No-start on Holley HP

 
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bobc455



Joined: 16 Jan 2015
Posts: 7

PostPosted: Mon Aug 31, 2015 7:40 am    Post subject: No-start on Holley HP Reply with quote

Hi-

Trying to help a friend with a Holley HP MPFI system on a Buick 455.

The engine will "kick" but then not run. So far I've checked the following:
- Spark exists
- Timing is correct (verified with timing light)
- Injectors have 12V+
- Injectors are being pulsed (verified with noid light)
- Fuel pressure is correct (43) with mechanical gauge directly in fuel rail
- Verified fuel flow by disconnecting a braided line on the intake manifold
- Verified mechanical operation (i.e. cam turns, valves open, compression, etc.)
- Verified it has good fuel
- Verified that the ECM is not fried (i.e. connected the laptop, watched RPM on dashboard during cranking, etc.)

So in essence, everything is there for the car to run- fuel, air, spark, etc.

Backround: The car was being backed out of a paint shop and died, and wouldn't re-start. It was an "electrical" type of cutoff (i.e. shut off immediately, no coughing or sputtering etc.). Since that, a new Map was sent by Holley and uploaded - the car ran for 5 minutes then died again and hasn't restarted since... We tried re-loading the old map, reloading the new map, etc.

If a car has fuel, air, and spark - why won't it run (or even try to catch)?

Some other information:
- Buick 455, built by a top Buick engine builder
- Car has been driven about 500 miles and has performed flawlessly until now
- MSD 6AL - with a tach adapter for the factory tach
- MSD distributor and Blaster coil (8202)
- Vaporworks fuel system with return-style regulator
- Accel fuel injectors (not certain of size but has a "24" stamped in the top)
- Dynoed at approx 540HP on a carb, approx 530HP on the FI system
- Tremec 5-speed
- No cam sensor (it seemed to be running in "paired" mode, although I would have put it in bank-to-bank)

Any thoughts appreciated, I don't understand why it would have died if fuel, air, and spark were all present.

-Bob C.
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David Ferguson



Joined: 21 Aug 2006
Posts: 59
Location: Paso Robles, CA

PostPosted: Mon Aug 31, 2015 10:59 pm    Post subject: Reply with quote

Did you verify all the ECU sensors? Bad MAP sensor or TPS if equipped might give those symptoms.

Injectors could still be clogged, pull one and check for debris in inlet screen. If that's the problem, they probably need a better final fuel filter (10 micron recommended).
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bobc455



Joined: 16 Jan 2015
Posts: 7

PostPosted: Tue Sep 01, 2015 5:24 am    Post subject: Reply with quote

Hi, Dave- Thanks for the thoughts. TPS was verified. I could only verify the MAP by reading the output on the dashboard (101kPA)- since the engine didn't run I didn't watch the MAP sensor for other values.

I had the same thought about the injectors. The injectors will be bench flow-tested next- we weren't 100% sure of the size, so I wanted him to confirm the flow rate anyhow. The injectors are stamped with a "24" but there's no way on earth he could have dyno'ed 540HP on 8x24# injectors.

But if it was clogged injectors, I can't imagine why the engine just stopped. It didn't cough & sputter, it just stopped like someone turned the key. And now it won't catch again.

There is a 10-micron filter before the pressure regulator but it wasn't clogged (enough to cause a problem anyhow) since I could verify 43 PSI in the fuel rails with the mechanical gauge.

To clarify- the engine will frequently catch for JUST an instant- if you watch the RPM during cranking the tach will go from about 110RPM to about 250RPM for just an instant, then back down to 110RPM. Perhaps a single cylinder fired or something.

I'm baffled on this one, so any other thoughts or things to double-check would be highly appreciated.
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stevieturbo



Joined: 29 Aug 2006
Posts: 1235
Location: Norn Iron

PostPosted: Wed Sep 02, 2015 2:58 am    Post subject: Reply with quote

If nothing whatsoever changed from it running fine to when it stopped running, then there should be obvious signs of a fault.

You say there is spark...are you sure there is a good repeatable spark on all cylinder the entire time you are cranking ?

What condition are the plugs in ?
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bobc455



Joined: 16 Jan 2015
Posts: 7

PostPosted: Wed Sep 02, 2015 4:14 am    Post subject: Reply with quote

Plugs had previously been removed and grounded against the frame, and I was told the spark looked fine (but didn't see this myself). I did put a timing light on the #1 cylinder to verify timing, and I also had it on the primary coil wire during cranking and the pattern looked even.

I agree that there should be an obvious fault somewhere- a bad relay, a fuel pump that doesn't run, a fried ECM that isn't communicating, etc., but I couldn't find anything irregular at all which is why I'm asking for other ideas, and hoping that maybe someone else has seen a similar no-run condition. Maybe there is a relay in the Holley systems that I don't know about, etc., that could be causing this.

Thanks for the ideas!

-Bob C.
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stevieturbo



Joined: 29 Aug 2006
Posts: 1235
Location: Norn Iron

PostPosted: Wed Sep 02, 2015 6:57 am    Post subject: Reply with quote

Check the plugs.

Check fuel is being injected.
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9.85 @ 144.75mph
202mph standing mile
http://www.youtube.com/watch?v=XgWRCDtiTQ0
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