Motorator Experts - Can anyone tell me the problem with my 5.0, it appears to have 4 week or dead cylinders. No 1, 2, 5 and 8.

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Question Category:

Mustang > Engines & Components > Valvetrain & Internal Engine Components

Can anyone tell me the problem with my 5.0, it appears to have 4 week or dead cylinders. No 1, 2, 5 and 8.

Engine has spark on all cylinders. I changed the injectors and switched the injectors around. The same cylinders are dead. I removed the exhaust from the manifolds. Still no effect. I checked the wires from the firewall plug to each injector for through current and all is good. I checked through current from computor plug through to firewall plug that leads to injectors and that checks out good. The fuel line and fuel pump ckeck out fine and fuel is pumped at good pressure. I put a high pressure air line in each cylinder while piston is at top dead center and there's no leaks. The car is a 95 mustang gt 5.0. I replaced the engine with a 1987 thunderbird 5.0 only using the block, rotating assembly, and heads(heads do have quite a bit small combustion chamber than 95 heads) all else and all electrical is from 95 HO engine.

Asked by: bill o

Asked on: August 13, 2008 22:19

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Answers

TheRipper (3 months ago)

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So you did a Compression test? It is hard to tell from the comment, but that would be first thing. Then check the firing order. I don't know much about the late model engines, but that would be easy to find out. Also check out things like the crank trigger, and related fuel injection stuff. I don't have much knowledge with stock stuff but might be something going on in that area. Last thing pull the valve covers and see if valves are working and at appropriate lift (at the valve) which is easily measured with ruler or dial gauge. Last thing do those head have any odd smog crap? And more details on what you mean by weak or dead, do you have any 'fire in the hole'? Might need others to comment but the more info the better. If you have fuel and a spark it should light up...

den1320 (3 months ago)

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Well the first thing I would check is what the firing order is for the engine you are using it may be different than the 5.0 mustang is, for that is a high output engine

gamera (3 months ago)

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I agree. Your problem is the wrong firing order. Running a 1987 motor with 1995 EFI electronics will not match. The fact that you have 4 cylinders out also indicates a bad firing order.

Refer to Motorator question #38 listed below. You're running the 5.0 HO firing order and you need to switch to the basic 5.0 firing order.

Motor8rMatt (3 months ago)

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Ripper, you're on the right track. A compression test would be the fist place to start. Pumping air into the cylinder is not the best way. Your compression tester will be a gauge with a hose coming off it that you can screw in where a spark plug goes. Turn the motor over a few times and see where the gauge goes. 5.0 Mustang/Late model EFI fords don't use a crank trigger. They use a TFI electronic distributor. However, the distributor, cap and rotor can still go bad, so check those. MSD makes replacements for all the ignition pieces. Lastly, I agree with Ripper on inspecting the heads. A bent valve could be causing a leak. Again, a compression test would discover this.

If you're concerned that the firing order is off, check out the link below to find the correct order.

References

http://www.motorator.com/questions/38
http://msdignition.com/product.aspx?id=5527 For 5.0 1987-1993
http://msdignition.com/product.aspx?id=5525 For 5.0 1994-1995 w/o Module

bill o (3 months ago)

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I'll tell you what i did last night regarding the firing order. I used the early model 5.0 firing order again. However, The timing was off 180 degrees different than that of the late model 5.0 so i re-set it then used the ealier (87) firing order. It fired right up and seemed to hit on all cylinders pretty good. However, according to the scanner, it was running real lean, 39 percent. Mind you i had the exhaust off. When i installed the exhaust the cat where glowing orange after running awhile.

bill o (3 months ago)

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After discovering further problem i now am going to install the 95 5.0 cam and the use the late model firing order. I am stumped!

bill o (3 months ago)

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Problem solved. I installed the 5.0 HO cam and used the Ho firing order. Runs good. thank you for all of your input.

TheRipper (3 months ago)

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Glad you got it sorted out. Sounds like firing order was the issue. One thing if you do a compression test and the car is a 4 speed, make sure you put the parking brake on or put the car in park so the engine does not crank. Do all compression test (for starters) at TDC for each cylinder if you do have to mess with it again. Good luck and if you have any more questions plenty of folks to help.