My 85 Down for the Count

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Sep 26, 2011 | 10:12 PM

rssshen vette

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From: Clarksville Tennessee

My 85 Down for the Count

My 85 Coupe has been down for the count for the past three months. To keep this post short and to the point I had a DFI installed back in July-August. When I go my car back it wasn't driveable. So I've set out to find and fix the issue. The issue Popping like back fire at idle. The fix was changing the firing order from GM HEI to DFI Sequenial. Another issue was low fuel pressure took care of that no problem. Now the car is hard to start and won't run for more that two seconds once I'm able to get is started. I think it's a problem with the timing. To check I set the #1 TDC; the rotor pointed to #1 plug wire; the Red and blue phase light were both on( Dual Sync dizzy). So I'm stumped at this point. What am I missing? Constructive helpful advice need. I live in newport news, va if there are any forum members in the area that can help me out over the weekend?

Sep 28, 2011 | 12:24 PM

jfb

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From: Cincinnati, Oh USA

Check the timing with a timing light.

Sep 28, 2011 | 12:43 PM

joe paco

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From: Louisville Ky

I don't believe it is timing issue if it starts -although it may be way off, retarded, most likely.

ck fuel pressure in the 2 secs it is running.

I would ohm injectors, possibly one near a dead short that will shut down the fuel enable in ecm.

chk tps, maf sensors by unplugging each one in turn to watch for a reaction. if tps signal is off, rich, ecm adjusts fuel to only 20%. *** not 20%, 20:1 air fuel ratio. brain error.
check at least a couple plugs for rich or wet.

Last edited by joe paco; Sep 28, 2011 at 07:46 PM. Reason: correction***

Sep 28, 2011 | 07:22 PM

rssshen vette

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Quote:

Originally Posted by jfb

Check the timing with a timing light.

Thanks guys for responding

I'm unable to check with a timing light at this time since it won't stay running long enough.

Quote:

Originally Posted by joe paco

I don't believe it is timing issue if it starts -although it may be way off, retarded, most likely.

ck fuel pressure in the 2 secs it is running.

I would ohm injectors, possibly one near a dead short that will shut down the fuel enable in ecm.

I need to go out and buy a volt meter.

chk tps, maf sensors by unplugging each one in turn to watch for a reaction. if tps signal is off, rich, ecm adjusts fuel to only 20%. check at least a couple plugs for rich or wet.

I'll unplug the TPS and see what happens. I don't use the MAF. The DFI is set up to run a Speed Density. The fuel pressure was low(25-30psi). I adjusted it to 40- 45 psi. Although the car won't run, each time I turn the ignition key to on position the fuel pump kick in and I'm able to see the fuel pressure reading at start up.
Two weeks ago it was able to start and run with no problem except for the back firing. Now this

Sep 28, 2011 | 08:02 PM

joe paco

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From: Louisville Ky

Quote:

Originally Posted by rssshen vette

Thanks guys for responding

I'm unable to check with a timing light at this time since it won't stay running long enough.

I'll unplug the TPS and see what happens. I don't use the MAF. The DFI is set up to run a Speed Density. The fuel pressure was low(25-30psi). I adjusted it to 40- 45 psi. Although the car won't run, each time I turn the ignition key to on position the fuel pump kick in and I'm able to see the fuel pressure reading at start up.
Two weeks ago it was able to start and run with no problem except for the back firing. Now this

not familiar with the DFI system you have. out of my experience league. but the TPI 91 uses the MAP, the IAT (MAT) and rpms, in speed density. I have heard of frequent issues with a FI shorting out, which puts the ecm in self protect mode, whatever, and ecm shuts down fuel to injectors. if you had HEI dist, several things in the system might do the same thing -according to fsm- hard start, but immediately dies.
sensors are: TPS, map and CTS. "additional" are iac, correct mem-cal.

Sep 28, 2011 | 08:57 PM

rssshen vette

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From: Clarksville Tennessee

Quote:

Originally Posted by joe paco

I'll doulbe check the map sensor. I re routed the vacum line going to it. It may not be getting any vacum.

Oct 1, 2011 | 03:05 PM

rssshen vette

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Latest update

There's no problem with fuel pressure or fuel getting to the cyclinder. The spark plugs saturated with fuel. I'm not getting any spark. I tested to see if I'm getting spark from the dizzy cap to the plug (No Spark). Then from the dizzy to the coil (got no spark). Lastly to tested to see if there is power to the coil from the MDS box.

Oct 2, 2011 | 08:55 PM

rssshen vette

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From: Clarksville Tennessee

My 85 down for the count UPDATE

I have power going to the MSD box but nothing coming out going to the coil. The good news about this is the MSD box I have had 3 days left on a 90 return policy at Advance Auto where I purchased it. So I was able to get a new box without coughing up more money

. Tomorrow I'll install the new box and go on from there. Hopefully there aren't anymore issues.