hyundai won't start after warm up

heyarn

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Make
hyundai
Model
santa fe
Year
2005
Miles
138000
Engine
2.7
2005 hyundai santa fe 2.7, 138,k miles, engine always starts when cold, then after it warmed up, will not start, you can drive it, just don't shut it off, the you will have a wait 30 min to an hour, the spark stays strong, always, the injector pulse goes very week with the noid lite, 12v side of the injector seems to stay solid around 12v, the signal voltage seems to intermittingly dissapear, then after cooling off, noid gets bright, then it starts, i think a wiring diagram from ecm to the injectors would be very helpful, thanks in advance for any help,
 

billr

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Do you have live-data? I would look first at ECT and IAT, then TP, MAP and injector PW. My guess is that there is a perception that the injector signal is getting "weaker" because the fueling is being commanded leaner and the injector pulse-widths are shorter.
 

heyarn

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thanks for the reply, i have live data, ect, iat tps, all look normal, here is a couple pictures, first one is cold start, started up , run 15 min, then the second pic is warm attemp to start, does not fire at all in the second pic
 

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billr

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A couple of things to try:

1) When it is warm and won't fire, try cranking with the throttle wide open. No joy? Then repeat that after giving it a quick blast of starting-fluid.

2) Connect a voltmeter to an injector power lead and check that it stays pretty solid at 12V as the injectors pulse.

Post similar logs with the MAP also shown.
 

heyarn

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no pid on this one for map, looks like there is no map on this one, ok voltage stays very close to 12 while crank on the injector red lead, cranked with throttle open, no change, shot of stater fluid, fires rite up,, thanks
 

billr

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Then look for MAF. Check fuel pressure when it cranks but won't fire. Does it keep running if you use the starting-fluid to get it firing?
 

grcauto

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Does the rpm register when it won't start? If not it's likely a crank sensor problem.
 

Mobile Dan

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Those temp sensor readings don't add up for me...
Cold start...42 intake and engine temp is already 123?
Warm start attempt after running 15 min...91 intake and engine temp is only 143?
 

billr

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Yeah, that caught my eye too, but I'm thinking the fueling at 143 should still be rich enough to get it to fire, since the fueling at "123" is rich enough for a cold start. And the fuel PW looked reasonable for a cold start and then a warm engine start.

On second thought, I agree with Dan and think we should investigate what seems like an ECT sensor problem before looking elsewhere. Check IAT and ECT after it has sat overnight. They should be within 5F of each other and the average should be within 5F of the actual ambient temperature. If this has an auto trans, then there is probably a trans-fluid temp sensor for a third reading.
 
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heyarn

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with a shot of starting fluid, it does start, and stays running fine, i haven't started the car today, i will get some temp readings from a true cold start, then i'll get back with pictures, thanks
 

heyarn

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it always shows engine speed when cranking, also a pid, on or off for a crank signal, shows on when cranking, cold eng and intake temps look normal, the first pic is key on, eng off, cold, the second pic is no start condition, eng is cranking after a very short warm up, less than 10 min
 

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billr

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The cranking speed looks low, and the MAF looks low. At 174 rpm cranking, with a 2.7L 4-stroke engine, I would expect to see 30-40 lb/hr for the MAF.
 

heyarn

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i just took a look at the maf, the intake tube is deterating, i squizzed it to see if it was cracked, my hand turned black, i'll take a closer look tomorow, thanks
 

billr

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Cleaning the grid on a MAF sensor seems to be a popular past-time, too. If no joy after fussing with the MAF sensor, check fuel pressure with a gauge.
 
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