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ELXR8 intermittent cold start problem (long) 

 

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 Post subject: ELXR8 intermittent cold start problem (long)
Posted: Thu Sep 08, 2011 4:45 pm 
Fordmods Newbie
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Joined: 17th Jan 2008

Location: Mornington
VIC, Australia

As per title, car has cold start issue, in that intermittently will crank for ages (1 minute or more) before starting. Usually starts almost immediately.
If it will occur (it doesn’t always) it only appears to be on a cold start, first thing in the morning, and only appears to occur if the car has not ran for 2-3 days (although sometimes after this period of time it will start without issue).
If the problem occurs, once the car eventually starts, if you turn it off it can be immediately re-started without issue.
I have checked for fault codes, and none are showing.

History of problem, and (attempted) fixes
Started approx 6 months ago. Without warning, one morning would not start. Simply cranked without even looking like it would fire. Could not drive to work at all.
That night troubleshooting suggested poor spark, so progressively swapped/replaced items to see if fixed (plugs, wires, cap/rotor, coil) and eventually when I replaced the TFI module it started right up. Problem fixed (or so I thought).

Approx 4 months ago, again extended cranking, (same thing in morning, sitting for 2-3 days) but this time started. As idle had been progressively getting worse (lower and eratic, and would not hold when put in gear for example), I thought that the ISC might be jammed, and not allowing any air to allow it to run. Replaced with the ISC off another TB and it stated straight up. Idle stable. Problem solved (or so I thought). I also checked/cleaned MAF wires (pretty clean), no change in problem when cleaned anyway.

Approx 2 months ago, again needed extended cranking, again cold start in morning, car sitting 2 –3 days. As I was running out of ideas, and appeared to only occur when not driven for 2-3 days or more, suspected maybe fuel issue (ie not holding pressure, or otherwise draining out of rails). Checked with fuel pressure gauge (did not have one previously, but when initially occurred I pushed in schroeder valve on rails, and fuel came out suggesting pressure in rails). Fuel rails would immediately pressurise when key cycled, and then hold for extended period of time with engine off. Pump always could be heard cycling in every previous event of this happening.

Approx 2 weeks ago, same issue. Extended cranking, but eventually started. Same condition, in that it was sitting for 3 days, and it was cold start in morning.

Difficult to troubleshoot, as it is intermittent, and always occurs when you are trying to get to work, so don’t have time to stuff around.

For info, car has ported iron heads, ported AU XR8 manifold, 2031 crane cam, 73mm vortec MAF (uses standard maf electronics – suit 19lb injectors), exhaust etc. MOds been on car for over 4 years. Has 250,000km on clock, still original injectors, fuel pump, distributor, and pretty much everything else (or other sensors) not mentioned above as already replaced. I don’t really want to replace anything else unless I have some idea it might be issue.

Hoping that someone might have had similar issue, and can suggest what might be problem
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 Post subject: Re: ELXR8 intermittent cold start problem (long)
Posted: Thu Sep 08, 2011 6:05 pm 
Getting Side Ways
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Ride: Lots, all Fords

Location: Hamilton
New Zealand

Do a wiggle test around the TFI plug. Even with a dead ecu you still get base timing spark output. That it doesn't fire suggests a problem with this circuit since you say you have fuel. I assume you did use plenty of heat sink paste on the TFI module?

If that doesn't help. Measure TPS voltage and set to 0.9V, no higher. Then try starting with a fraction of throttle on the gas pedal.

 

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XA Faimont 351C, AU2 XR8 Manual 5.0, DA LTD 5.0, Mk1 Capri 5.0, 1995 Mustang 5.0, EF2 XR8 Manual, EF2 Fairmont Ghia 5.0, AU3 XR8 Auto, AU2 XR8 Auto, AU2 XR8 Manual Ute, TE Cortina 5.0 Manual, DU LTD 5.0 soon to be manual

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 Post subject: Re: ELXR8 intermittent cold start problem (long)
Posted: Fri Sep 09, 2011 1:12 pm 
Fordmods Newbie
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Joined: 17th Jan 2008

Location: Mornington
VIC, Australia

When you say "wiggle test", do you mean try wiggling the wires at/around the plug to see if it makes a difference ? (ie check continuity through plug and see if wiggling changes) ?

Yes, used plenty of heat sink paste on TFi mod.

I will check TPS as you suggest too.

Appreciate your advice.
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 Post subject: Re: ELXR8 intermittent cold start problem (long)
Posted: Fri Sep 09, 2011 4:51 pm 
Getting Side Ways
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Posts: 699

Joined: 1st Jan 2006

Ride: Lots, all Fords

Location: Hamilton
New Zealand

If you have access to a Ford tester you can run a diagnostic check while wiggling the wires (called the wiggle test). Without the tester you just have to wait until it faults, then wiggle those TFI wires, then try and start, repeat as necessary. You should know in 5 minutes if this is the cause

Set the TPS voltage while the engine is running as Vref often rises when the alternator is charging. The cranking with slight throttle will help determin ISC circuit problems. The early EF V8 ecus had lots of ISC driver failure problems. I have a 4DEF ecu where the ISC driver only works sometimes. But I've never heard of problems with EL ecus. However it's still worth checking given your symptoms

 

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XA Faimont 351C, AU2 XR8 Manual 5.0, DA LTD 5.0, Mk1 Capri 5.0, 1995 Mustang 5.0, EF2 XR8 Manual, EF2 Fairmont Ghia 5.0, AU3 XR8 Auto, AU2 XR8 Auto, AU2 XR8 Manual Ute, TE Cortina 5.0 Manual, DU LTD 5.0 soon to be manual

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