Zero Compression - why?

Treachery · 05-05-2004, 01:44 PM

After driving off the freeway, my '93 GT started to shake as if it had a vacuum leak. The car will then not start unless I pump the pedal.

Then it starts, the idle is VERY rough , the car would shake and the engine would die. I checked the hoses, replaced the EGR and fuel filter but the problem was still present. In order to get my Mustang to idle, I needed to increase the fuel pressure and TPS voltage.

I took my car to my mechanic and he did a compression check. He found that there was ZERO compression on each cylinder on the passenger side.

What would be the cause of this? Blown head gasket? Valves?

As the engine is being disassembled, what more can i expect?

420nitro · 05-05-2004, 09:21 PM

Bent valves on that side.
Did you see any smoke before or after it runs?

blue oval 50h · 05-05-2004, 10:18 PM

Like Nitro said, sounds like bent valves

A leakdown tester will pinpoint area

Treachery · 05-06-2004, 06:17 PM

There was no smoke. Mechanic said maybe the "lifters"? Hasn't looked at it, yet.

~The Jester~ · 05-07-2004, 06:24 AM

Nothing against your mechanic, but if the lifters were bad, they'd make a hell of a lot of noise, and they would also tend to keep the vavles CLOSED. Hydraulic lifters collapse and get shorted when they go bad. If you have zero compression, the lifters would have had to "grow" to hang the valvles open.

I'm with nitro too. Probably jumped the timing chain a tooth or 12, and bent the valves on that side.

BLACK85GT · 05-07-2004, 06:44 AM

I had a similar problem before, and it was 2 bent valves. Make sure he checks the spring pressures before reassembly.

Treachery · 05-07-2004, 06:12 PM

Thanks.

If problem is indeed valves.. What brand would be considered top quality? Whatever is done on that side, i'm going to have done on the other side regardless. If the valves need replacing on the bad side, i'm going to have them changed on the other side as well..

I know.. more $$$.. but it's a personal superstition, i guess.

BTW- you ever notice that when your Mustang is out of commission, you see more hot rods on the street than you would if you Mustang is running?

84LX89GT · 05-08-2004, 11:18 PM

what caused the valves to bend? I'd replace the timing chain and gears while it's down.

StangFlyer · 05-09-2004, 12:14 AM

Quote:

Originally posted by Treachery
BTW- you ever notice that when your Mustang is out of commission, you see more hot rods on the street than you would if you Mustang is running?

Amen to that... it's so very true. Not only that, but it always seems all the good stuff comes up that you could have taken your Mustang to (shows, races, etc) when it's out of commission too. Ahhh, such is life I guess...

Regardless, I am in the same boat as you actually. I seriously over revved my engine accidentally during the NMRA World finals last fall (probably to 10,000+ RPM) and I bent ALL the valves in my engine. Every cylinder pumps zero except number 6, which only pumps 90 psi. OOOPS. So, with the weather quickly warming up I am about to start ripping the motor out, and down, to change out all the valves, check the rest of the heads over, check the bearings.. etc... and set everything back up for the season.

05-05-2004, 01:44 PM	#1
Treachery Registered Member Join Date: Jul 2002 Posts: 38	Zero Compression - why? After driving off the freeway, my '93 GT started to shake as if it had a vacuum leak. The car will then not start unless I pump the pedal. Then it starts, the idle is VERY rough , the car would shake and the engine would die. I checked the hoses, replaced the EGR and fuel filter but the problem was still present. In order to get my Mustang to idle, I needed to increase the fuel pressure and TPS voltage. I took my car to my mechanic and he did a compression check. He found that there was ZERO compression on each cylinder on the passenger side. What would be the cause of this? Blown head gasket? Valves? As the engine is being disassembled, what more can i expect?

05-05-2004, 10:18 PM	#3
blue oval 50h Registered Member Join Date: Dec 1998 Location: NJ Posts: 219	Like Nitro said, sounds like bent valves A leakdown tester will pinpoint area __________________ 347- 10.63@128 N/A

05-07-2004, 06:24 AM	#5
~The Jester~ Rat Killer Join Date: Aug 2002 Location: Cold ass Ohio Posts: 1,143	Not lifters.... Nothing against your mechanic, but if the lifters were bad, they'd make a hell of a lot of noise, and they would also tend to keep the vavles CLOSED. Hydraulic lifters collapse and get shorted when they go bad. If you have zero compression, the lifters would have had to "grow" to hang the valvles open. I'm with nitro too. Probably jumped the timing chain a tooth or 12, and bent the valves on that side. __________________ d-Con Racing "Nothing fancy, just 347 inches of RAT POISON!" MICE need not apply.....

05-07-2004, 06:44 AM	#6
BLACK85GT Registered Member Join Date: May 2002 Location: Tampa,FLORIDA Posts: 340	I had a similar problem before, and it was 2 bent valves. Make sure he checks the spring pressures before reassembly. __________________ 5.0, Holley heads, 1.7 Scorp Rockers, Stealth intake, Holley 600 carb, Holley Mech. Fuel pump, MSD 6Digital, MSD distributor, Hotchkis upper/lower rear control arms, FMS B Springs, 3:73 (8.8) rear. Production # 9,377

05-08-2004, 11:18 PM	#8
84LX89GT Mustangs Join Date: Jul 2000 Posts: 1,938	what caused the valves to bend? I'd replace the timing chain and gears while it's down. __________________ 2005 Suzuki Hayabusa GSX1300-R 1980 Ford Thunderbird - 255 V8 ported heads, 5.0L ported stock headers, O.R. H-pipe and Flowmaster 2-chambers, dual roller timing chain hi-po Mack Truck hood emblem 1985 Mustang GT 5.0L T5, F-303, GT40p, headers, off-road h, flowmasters, MSD stuff, etc. Sold 02/06/04 1989 Mustang GT ET: 13.304@102.29 mph (5-24-03) Sold - 1998 Mustang Cobra coupe, 1/4 mile - street tires: 13.843@103.41 (bone stock)

05-05-2004, 09:21 PM	#2
420nitro Registered Member Join Date: Nov 2003 Location: Rockford Posts: 596	Bent valves on that side. Did you see any smoke before or after it runs?

05-06-2004, 06:17 PM	#4
Treachery Registered Member Join Date: Jul 2002 Posts: 38	There was no smoke. Mechanic said maybe the "lifters"? Hasn't looked at it, yet.

05-07-2004, 06:12 PM	#7
Treachery Registered Member Join Date: Jul 2002 Posts: 38	Thanks. If problem is indeed valves.. What brand would be considered top quality? Whatever is done on that side, i'm going to have done on the other side regardless. If the valves need replacing on the bad side, i'm going to have them changed on the other side as well.. I know.. more $$$.. but it's a personal superstition, i guess. BTW- you ever notice that when your Mustang is out of commission, you see more hot rods on the street than you would if you Mustang is running?

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