Question about 6.9 hard starting and lack of power - Ford Powerstroke Diesel Forum
6.9L IDI Diesels Technical discussion of topics related to vehicles powered by the 6.9 Liter In-Direct Injection Navistar engines.

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Old 12-08-2010, 05:10 PM
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Question about 6.9 hard starting and lack of power

The local dog groomer has a 6.9 IDI that is hard to start and lacks power. I thought I'd kill an afternoon and try to help out.

Do these engines have a glow plug relay that could be shot? Is it easy to access and test with a voltmeter?

Can I test the glow plugs with an ohm meter without removing valve covers?

Any other suggestions of what I could check that would cause hard morning starts or lack of power?

Thanks!!

Mark.

Last edited by torq; 12-08-2010 at 05:11 PM. Reason: edited for clarity
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Old 12-08-2010, 05:22 PM
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6.9 IDI the glowplugs are installed into the heads like a sparkplug, Also the injectors are external of the valve covers too. It has an injection pump on the top of the engine it is driven by a cam gear off the timing gears.

This engine is nothing like a 7.3L psd that is under the hood of your truck.

I strongly suggest getting a manual on this truck and engine.

Hard starting lacking power, start with fuel filter, poor fuel supply will cause this. If it is running rough you can crack open each fuel line at the injector. Listen for an unchanged sound while the engine is running. If you do hear a change in the engine running then tighten that injector line. Then move onto the next injector line.
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Old 12-08-2010, 08:42 PM
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Quote:
Originally Posted by bigcountrysg View Post
6.9 IDI the glowplugs are installed into the heads like a sparkplug, Also the injectors are external of the valve covers too. It has an injection pump on the top of the engine it is driven by a cam gear off the timing gears.

This engine is nothing like a 7.3L psd that is under the hood of your truck.

I strongly suggest getting a manual on this truck and engine.

Hard starting lacking power, start with fuel filter, poor fuel supply will cause this. If it is running rough you can crack open each fuel line at the injector. Listen for an unchanged sound while the engine is running. If you do hear a change in the engine running then tighten that injector line. Then move onto the next injector line.
That's great, thanks for the help! Sounds like a much older design and the manual suggestion is a good one. I'll pass a link to your suggestions on to the owner.

Mark.
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Old 12-09-2010, 08:27 AM
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Quote:
Originally Posted by torq View Post
That's great, thanks for the help! Sounds like a much older design and the manual suggestion is a good one. I'll pass a link to your suggestions on to the owner.

Mark.
No problem man, you may also want to check fuel supply if the fuel filter does not resolve the problem. You may want to see if it is getting ample supply of fuel. You may need to drop the tank and check the fuel sock in the tank. Being it is an older truck the fuel sock may be clogged up and needs replacing.

Or it may need new injectors, or the fuel injection pump may not be supplying the proper fuel pressure to the injectors.
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Old 12-09-2010, 09:08 AM
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Good info already. Also, this is a N/A IDI, they are rated 170-175hp from the factory...so they are going to be underpowered.

If you can get it to start, tell us what kind of smoke it makes. White, black, grey, blue. 6.9's have a crappy controller that likes to fail in the on position, so it fry's the glow plugs. I was lucky enough to have it fail in the off position. Only use motorcraft/Beru glow plugs, ONLY!

Also, timing can play into hard starts/low power, that would indicate retarted timing.
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