Cranks but does not start

Tiny
ROPER031
  • MEMBER
  • 2004 ISUZU RODEO
  • 3.5L
  • V6
  • RWD
  • AUTOMATIC
  • 136,000 MILES
Vehicle will crank just fine but wont start. Have replaced both cam sensors, crank sensor, high pressure fuel pump, fuel pressure sensor, new computer, new ignition switch. Checked timing belt and timing marks and verified cams are turning properly. Any suggestions would be awesome.
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Monday, November 21st, 2016 AT 1:14 PM

10 Replies

Tiny
CARADIODOC
  • EXPERT
Bad gas? We had two cars come in on tow trucks a number of years ago for the same symptom. Cam timing, spark, fuel pressure, and compression were all okay. After a day and a half of banging his head on the wall, the very experienced mechanic threw a gas sample on the floor, then threw a lit match on it. The "gas" put the flame out. Found out both owners had just bought gas from the same gas station. Drained and refilled both gas tanks, and the drivers buzzed off into the sunset with no further problems.

If you have a fuel pump relay, remove that, then try starting the engine with starting fluid.
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Monday, November 21st, 2016 AT 4:21 PM
Tiny
ROPER031
  • MEMBER
Will try that.
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Monday, November 21st, 2016 AT 5:52 PM
Tiny
ROPER031
  • MEMBER
Let you know in a little bit.
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Monday, November 21st, 2016 AT 5:52 PM
Tiny
ROPER031
  • MEMBER
Okay drained gas and it was still highly flammable. Spayed starting fluid in the hose for brake booster and it did start, but did not run very good at all for a couple of seconds.
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Tuesday, November 22nd, 2016 AT 11:26 AM
Tiny
CARADIODOC
  • EXPERT
Well, I guess we know you have spark!

One thing to consider is by removing that large hose, you created a large vacuum leak. On almost all cars except for Chrysler products, the mass air flow sensor has the biggest say in fuel metering calculations. That is done by measuring the weight of the incoming air. There can never be any loose hose clamps, cuts in the fresh air hose, or other leaks that allow air to sneak into the engine without going through that sensor. Air that does not get measured won't get fuel to go with it. That can explain the running, but running poorly.

Where I would start now is by viewing live data on a scanner to see what the Engine Computer is seeing. In particular, does the mass air flow sensor's readings look normal? Also check the diagnostic fault codes. Those can give us a better idea of where to start.
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Tuesday, November 22nd, 2016 AT 4:23 PM
Tiny
ROPER031
  • MEMBER
Just wanted to update yall. I found a broken pin on the cam shaft pull your that made the driver side cams get way out of time and bent a couple of valves. Have the heads at the shop now being repaired
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Saturday, November 26th, 2016 AT 7:54 PM
Tiny
KEN
  • ADMIN
Nice work, we are here to help, please use 2CarPros anytime.

Best, Ken
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Saturday, November 26th, 2016 AT 8:15 PM
Tiny
CARADIODOC
  • EXPERT
Don't know how you found that, but I'm happy you did. Chrysler had a similar problem in the '90s with their single-cam Neon engines. On those, the Engine Computer will set a diagnostic fault code for "Cam and crank sync" when the timing belt jumps one tooth. It turns on the Check Engine light too. At two teeth off it shuts the engine down to protect the valves. There's your no-start, even though you have good fuel pressure, and often intermittent spark. At three teeth off, the valves can be bent.

There is a dowel pin between the camshaft and its sprocket, and that can shear off and allow the sprocket to rotate over time. That results in late valve timing, just like when the timing belt jumps a tooth, but investigation shows the sprockets' timing marks are right on. I spent days trying to find the first one. Now I learned that was a common problem.

Can I guess that before the crank / no-start occurred, there were other engine running symptoms that might have been a clue this was about to happen?
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Sunday, November 27th, 2016 AT 8:00 PM
Tiny
ROPER031
  • MEMBER
Not what you like to see
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Sunday, November 27th, 2016 AT 8:49 PM
Tiny
CARADIODOC
  • EXPERT
"Darn the bad luck"! Maybe you could spin them around or pound them flat? What about switching the top ones with the bottom ones? I wonder if stronger springs would pull them closed.

I hope you're laughing at my sad suggestions, but I've heard such things before, ... From mechanics!

Hope to hear soon it's running and you're ready to buzz off into the sunset.
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Sunday, November 27th, 2016 AT 8:57 PM

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