Hot start issues.. STILL

91 XR7

Registered User
Yep tht's right, my '91 SC still has a Hot start issue, and it's now driving me nuts.. I know i bought this car for a challenge but DAMN!!

Replaced with NEW:
Sparkplug
Sparkplug wires
Fuel Filter
Cam Sensor
DIS module
ECT sensor
TPS (?? I think i did?)

On the car is a '93 PN (Read OE Ford) Crank sensor that looks to have been replaced recently (IE Loom is clean, Wires clean Sensor itself clean), Balancer is looking good with no cracks in the rubber, and spins straight..

Fuel Pressure is good, 40ish KOEO and 30ish KOER (Mechanically 100PSI guage) FP held good, after like 30-45 minutes it was still in the mid 20 PSI range, instanly came up when key was turn to run, and stayed good during cranking and starting..

When Cold the car starts great, sometimes with in a quick hit of the key.. once warm it can take like 5 or more seconds of turning it over to get it to start.. with the odd times it running at around 400rpm, and if left Black smoke will start coming out of the exhuast and it can run like that for some time.. with out throwing a code either!!!! But usually if you press the gas pedal a hair, and it gets up to like 500-600RPMS it'll catch fully and go up to like 1500rpms and settle back down to it's proper RPM like if nothing happened :eek:

Ground issue? Even thou i upgraded the factory grounds (4ga from battery to chassis and chassis to engine along with Battery to Alternator (Ground and Postive))
MAF sensor?? Down side i have no spares unless one from a '89 XR7 will work?
O2 Sensors?? (like it reads those for the first few seconds of running)
ECU itself??

Thanks
 
Do you have vacuum leaks? What is your vacuum? Check our your PCV valve. Clean it up and make sure it rattles.

Another possibility is the coil on the DIS.
 
vacuum is around 20 inches of Mercury at idle, I've haven't double checked it with an Test gauge thou..

And I've recently went through everything to reseal everything, replaced a few hoses since i didn't like the looks of them (seemed to be okay, but questionable)

The PCV was good and clean too.. (checked it when i had the SC off doing the snout seal)

Also tried a different coil with out any change..
 
and if left Black smoke will start coming out of the exhuast and it can run like that for some time..

im thinking with the black smoke there might be the possibility of a crack in the head/heads or a bad spot on the head/heads gasket. it almost seems like your problem is when it get warm threw expansion you might be getting some oil in the cylinders, KEEP IN MIND THIS IS JUST A THOUGHT! so dont panic. what did your recent plugs look like, is your oil staying at proper level, is your coolant clean or is it turning orange. if all those things are ok then you can most likely rule out head problems. i will say at times mine dips to low rpm when starting out at warm to hot temp, it goes away in seconds. from what ive gathered its my egr going out. that might be something to look at to.
 
Coolant level and color is good..
There is oil loss, but it does have 110,000 miles on it.. in 3,000 miles i've added like 2 pints?
Spark plugs other then Worn looked good.. Not oiled or carboned up..

The car did fail emissions testing twice in it's life, and has `new' Cats in it (crudely installed) But when i had it tested it passed with flying colors, differently better then my '96 XR7 with a 4.6L :)
 
black smoke

black smoke is always too much fuel, white smoke can be coolant or oil, oil smoke will have blue tinge and stink, I'd be looking for fuel burn/mix problem.
90 SC owner
 
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I'm certain that is running rich when it does it's lumpy 400RPM idle, since it does have that typical rich smell..

I'll be checking over the wiring soon enough.. i may even try running a 14Ga ground to select areas of the ignition system for a better grounding.. I'm just suprised with all the issues these cars have had.. no one has had this one or knows a fix to it.. In the local club i hand out with.. there is another SC owner with the same hard to start when hot issue as mine...
 
wow my car started doing the same thing about a week ago. starts up great when cold, but when the engine is hot, it actually doesnt start at all. i went to the store to grab something and when i got back in my car, it just cranked and cranked, i could hear the fuel pump running, and my upshift light was off.let is sit for about an hour and when it finally started idle was real low and car was running extremely rich, accelerator would not respond and then it just "catched" by pumping the pedal and all was normal on the drive back home. i shut it off and tried to restart,but again it wouldnt start. ive been driving it to work like that, since it turns on good when cold, and runs without any problems. when i have time i will try to track down the problem, i have a feeling that it is spark related, possibly something causing spark to be weak or out of time. mine should be easier to figure out than yours since mine does not start until the engine has cooled back down for at least an hour, so that gives me a bigger window for testing than your 5 seconds of extended cranking.
 
Next time you go to start the car hot, hold the gas pedal to the floor while cranking for a couple of revolutions then take your foot off of it.

Fraser
 
Yep tht's right, my '91 SC still has a Hot start issue, and it's now driving me nuts.. I know i bought this car for a challenge but DAMN!!

Replaced with NEW:
Sparkplug
Sparkplug wires
Fuel Filter
Cam Sensor
DIS module
ECT sensor
TPS (?? I think i did?)

On the car is a '93 PN (Read OE Ford) Crank sensor that looks to have been replaced recently (IE Loom is clean, Wires clean Sensor itself clean), Balancer is looking good with no cracks in the rubber, and spins straight..

Fuel Pressure is good, 40ish KOEO and 30ish KOER (Mechanically 100PSI guage) FP held good, after like 30-45 minutes it was still in the mid 20 PSI range, instanly came up when key was turn to run, and stayed good during cranking and starting..

When Cold the car starts great, sometimes with in a quick hit of the key.. once warm it can take like 5 or more seconds of turning it over to get it to start.. with the odd times it running at around 400rpm, and if left Black smoke will start coming out of the exhuast and it can run like that for some time.. with out throwing a code either!!!! But usually if you press the gas pedal a hair, and it gets up to like 500-600RPMS it'll catch fully and go up to like 1500rpms and settle back down to it's proper RPM like if nothing happened :eek:

Ground issue? Even thou i upgraded the factory grounds (4ga from battery to chassis and chassis to engine along with Battery to Alternator (Ground and Postive))
MAF sensor?? Down side i have no spares unless one from a '89 XR7 will work?
O2 Sensors?? (like it reads those for the first few seconds of running)
ECU itself??

Thanks

Was the ECT you replaced new? If not get a new one.
 
ECT was replaced with a Brand new Ford piece..

Fraser, i know i've tried pushing the gas pedal some while cranking it over (never to WOT thou:confused:)

Usually i try to start it, it does it typical hot start crank, i open the throttle some (1/2 or so) it still does just cranks over for another few rotations then it finally catches and i instantly let off the throttle it revs up to 1500rpm like normal.. i do not know if it truely did something or it's just coincidence.. since it's still in the same kinda overall time frame as if i didn't push the gas pedal.. but never does the 400RPM black smoke idle thou..

Mam.. one day we'll figure this out :) Either that or i'm personally parting out this thing when the insurance is up :p Hey i need a Parts car to fix up my '91 XR7.. i just hope the rockers in the rear are good.. BAH!!!
 
Holding it to the floor shuts the injectors off. I'm just curious to see if its because your flooding out or some other reason.

Fraser
 
You may have a plugged or leaking fuel injector or some type of injector problem. Also may have some carbon buildup on valves.

Without diagnostic testing I can't be for sure, but it wouldn't hurt to run some good injector/combustion cleaner.
If you decide to do that don't use the crap that you pour in your fuel tank; use the one that connects to your fuel rail and turn off the fuel pump.
 
I had the same problem years ago. I did the flooring it before start and it fired up every time. When I took it to Vernon he said it was a temp sensor. When that one goes out it says it tells the computer that its really cold and to dump more fuel. After it was changed out I have had no problems in years. Dont know if that will work for you but it did for me.
 
Fraser; I knew what flooring the throttle does during starting :p
After work today after like 3-4 compression strokes it wasn't starting, so i floored it and within like 3 compression strokes it started... There be a fair amount of Stopping tomorrow so i can do more `testing'

How long should the fuel pressure stay good for after the key is off?? dropping like 10-12? PSI in like 30-45 minutes bad?? The injectors had been cleaned and checked (professionally) and even before i stuck them into the intake i installed them onto to fuel rail and powered up the car, jumped the FP turn on lead at the Self test connector, and ran it at that for like 5minutes without a drip.. :confused: Unless for some reason only when they are warm they leak?

Silenced; I can try to figure that out in the next day or two.. I know it's charging in the normal range when running good thou..

speed95; As i stated In the first post, that was one of the Sensors i replace (Ford unit too)

Another thing is, the car does have to sit for like 10-15 minutes (on average) for it to start to do this.. and the longer it sits the worse it gets so it really is a heat soak kinda deal.. I can shut it off and restart right away with no problems.. even after a few minutes..
 
Silenced; I can try to figure that out in the next day or two.. I know it's charging in the normal range when running good thou..

Check it please. You're getting too much fuel without good reason. If voltage is low, strange things can happen... When you rev the low idling motor, you are in turn spinning the alternator faster, increasing its propensity to charge the system and correct the voltage (if it is low).
 
The other thing that can be happening is that exhaust is being sucked into the intake at shutdown diluting the air/fuel charge at startup unless the car sits for awhile. My car does that because of valve overlap caused by the cam and I can tell when its going to happen by watching the pressure gauge. If it suddenly goes to zero, my next startup needs to be throttle to the floor.... if the gauge gradually goes to zero, then all is well.... if I don't because the car doesn't start right away it gets flooded out. Spin the motor a couple of times with injectors off purges the garbage out and away you go.

As for voltage, the EEC compensates for lower voltage by increasing pulse width to the injectors. If it didn't then the injectors wouldn't be supplying enough fuel at lower voltages.

Fraser
 
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