Missing bad under load. Where to start???

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JamesRR

JamesRR

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I have a Duster that is purely a strip car. 500ci, b1 heads, 13.8-1 compression, holley 1250 dominator, roller everything, electronic everything, no belts and pulleys. This weekend took it out and it was missing badly at higher RPM (4,500ish-up) while under load. Never had this happen before. Have made 15 passes and car drives like it stole something. Did not seem to do this in neutral. I seemingly lost fuel pressure at one point. Gauge read 0 when it should have been at 5. Turned the car off and made sure all the wires for the gauge were connected and hadnt rattled loose. Fired car up and the gauge read normal at 5. made another pass and had the same miss with the fuel pressure reading normal. Do you think this is a fuel issue or an ignition/electronic issue? Fuel/air? bad carb gasket? any help is appreciated. Thank you.

James :banghead:
 
I'm gonna think timing Check rotor cap,distributor.
 
Check all of the above first.

Check ground on electric fuel pump, if you're using one.

Do not know location of fuel pressure gauge sending unit. Check ground on it. Check fuel lines between sending unit and carburetor and eliminate kinks.
 
I'd say it's possible your spark is cross-jumping across terminals in the dist. cap or jumping out of the spark plug wires, maybe onto a header or valve cover when under a load. Make sure you've got good clearance from S.P. wires/ground sources.
 
Put a diagnostic fuel pressure gage on it and verify if the gage is right. Reading the plugs should tell you if it's leaning out or detonating. Check the connections for the ignition's power source and the coil connections.
 
One other thing.
Hot ignition systems can and do burn the core out of some types of spark plug wires.
Under a load is where it is noticed first..
Chk where the contact is crimped onto the plug and look for burn marks in the center of the wire where the core is. (or was)
 
The coil is a likely candidate but don't kill me if I'm wrong. The age of all the components is what's in question here as far as where to start to. The coil wire itself I have also seen do what you're describing and loose pos and neg wires at the coil to.
 
ANYTHING in the entire ignition could cause this, from low primary supply voltage, to any deterioration in the hi V. end.

I'd be tempted to swap in as much different ignition (the entire system) as you can, and if it cleans up, THEN you know that it's "in that system" somewhere and can start looking. Be absolutely sure to verify good primary voltage.

Could be as simple as a bad coil wire, plugs, dirty/ carbon tracked cap/ rotor. Rotors can be tricky. I've see (black) rotors "punch through" and you could not SEE it without a strong light and magnifier
 
I'm thinking it's a fuel issue.
Check your filters and pump to see if it's flowing at what it's rated for.
Water in the fuel can cause a lot of insane problems too.
 
I noticed some coolant dripping towards the rear of the engine. It was on the starter. Trying to trace it. If its a head gasket Im guessing this could very well be it. Who makes head gaskets to withstand 14:1 compression?

J
 
Sounds like a bad ground -My Duster Race car would mis-fire and stubble after sitting a few weeks and for some reason the ignition ground would always be it.
How old is the fuel also?
Head gaskets -Cometic , just follow the surfacing instructions
http://www.cometic.com/
 
dwire67 said:
Sounds like a bad ground -My Duster Race car would mis-fire and stubble after sitting a few weeks and for some reason the ignition ground would always be it.
How old is the fuel also?
Head gaskets -Cometic , just follow the surfacing instructions
http://www.cometic.com/
Click to expand...

Fuel is a couple of weeks old and we run 116. It sat prior to us owning the car but we took it out twice with no issue. Thanks.

J
 
bOb shingler said:
when it's missing a full load what happens when you take your foot out of it some but not the whole way?
Click to expand...

seems to drive ok when when at half throttle but I didnt really wind it out with less throttle. I got it to 3rd and just kind of cruised. Again I only made 2 passes like this due to the fact I didnt want to damage anything.
 
5 psi with a Dominator?

I'll go fuel delivery issue.

Turn it up to 7.5 and try again.
 
Spark mis-fire is much more likely at WOT and low speed, where the cylinder pressures are highest. A spark jumps a gap much easier at low pressure. My 2.4L did that until I decreased the spark gap to 0.045", based on a Mopar bulletin for the turbo engines (mine isn't).

However, you can't "feel" whether it is due to spark or fuel. I have had starved fuel conditions that feel exactly the same.
 
JamesRR said:
seems to drive ok when when at half throttle but I didnt really wind it out with less throttle. I got it to 3rd and just kind of cruised. Again I only made 2 passes like this due to the fact I didnt want to damage anything.
Click to expand...

check out the bulkhead connectors for corosion, especially the main feed.
 
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