The engine cranks but will not start unless spark plugs are removed?

Tiny
JOHN ENGEL
  • MEMBER
  • 2004 FORD EXPLORER SPORT TRAC
  • 4.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 250,000 MILES
Truck will only start when I remove cylinder 2 and 3 spark plugs. How do I fix this?
Monday, September 1st, 2025 AT 11:15 AM

7 Replies

Tiny
MECHTRIX
  • MECHANIC
  • 382 POSTS
Sounds like the classic blown head gasket. Check the compression in those 2 cylinders to see they could be leaking between them.
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Monday, September 1st, 2025 AT 8:16 PM
Tiny
MECHTRIX
  • MECHANIC
  • 382 POSTS
Did it over heat before this ? Any codes or check engine light on the dash?
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Monday, September 1st, 2025 AT 8:17 PM
Tiny
JOHN ENGEL
  • MEMBER
  • 2 POSTS
No. I did compression check. Number 3 is at 130 PSI all others are 185 psi. Would this indicate head gasket?
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Thursday, September 4th, 2025 AT 8:43 AM
Tiny
MECHTRIX
  • MECHANIC
  • 382 POSTS
Probably not blown but not sure yet take the cap off and check the radiator see if theres any milky Sludge in the filler neck
Also check the oil for the same Sludge on the stick if theyre clean let me know also it would be great if you could post a photo here. Let me know thanks good luck
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Thursday, September 4th, 2025 AT 3:53 PM
Tiny
MECHTRIX
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There are a few things that can cause this problem we can work to rule them out. Is it possible someone crossed the coil plugs on numbers 2 and 3?
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Thursday, September 4th, 2025 AT 3:56 PM
Tiny
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Also when is the last time it was running well?
Was any work performed since then?
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Thursday, September 4th, 2025 AT 3:57 PM
Tiny
MECHTRIX
  • MECHANIC
  • 382 POSTS
You truck came with 2 different coil types
1. Coil on plug type (each plug gets its own coil )
And
2. Coil pack ( a block wich all 6 wires plug into )

Wich type does yours have ? Description 1 or 2.?
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Thursday, September 4th, 2025 AT 4:04 PM

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