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94 ford aerostar wont remain running
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farnold
New User
Feb 17, 2009, 9:00 PM
Post #1 of 11
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94 ford aerostar wont remain running
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Hi, I am new to this forum and have a problem with my 94 ford aerostar 4.0 liter engine. It keeps dying on me. I had it towed to a shop and the shop (who rebuilt the motor under warranty) are telling me that they think that the oil pressure (measured at 100 lbs) is causing the lifters to not pump up and keeps stalling the van.
They have taken the heads off 3 times (and it stalled 3 times) and said that this is what they finally believe is the problem. I am about fed up with them and it doesn't sound right to me. What do you think? Any ideas.
The motor was completely rebuilt 9 mos ago.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 17, 2009, 10:03 PM
Post #2 of 11
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Re: 94 ford aerostar wont remain running
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?? 100psi for oil pressure is unusually high! There are by-passes to disallow excessive oil pressure so I think you probably have that # wrong but not the issue for now.
What's the warranty on the engine overhaul?
If this is a mechanical fault and not just a fueling or spark issue it should be under some warranty. I don't understand removing the heads THREE times in some effort to fix or diagnose this??
Can you get a second professional opinion on the engine job?
T
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Loren Champlain Sr
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/ Moderator
Feb 18, 2009, 6:45 PM
Post #3 of 11
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Re: 94 ford aerostar wont remain running
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I think you may be meaning that the lifters are being pumped up. This would cause the valves to hang open causing a loss of compression. As dmac stated, 100 psi is waayyy too much. What weight oil are you running. Should be 5W30 or no more than 10W30. There are some engines that will not even run with 10W30 because it will cause the lifters to pump and hold the valves open. The oil pump has a check valve to control the pressure.
Possibly, a defective pump?
Loren
SW Washington
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farnold
New User
Feb 18, 2009, 8:59 PM
Post #4 of 11
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Re: 94 ford aerostar wont remain running
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Thank you for the response. Yes you are right the oil pressure is 100 lbs, I couldn't believe it.  The shop owner is pulling off the oil pump and replacing it. He told me that there is no compression and it sounds like the lifters are keeping open the valves, which is completely new to me.
The engine has a 1 year warranty and it broke down 3 times in the past 9 months which the shop believed was a valve problem and kept pulling the heads because it would die and "pop." They then had the heads checked 3 times to find nothing really wrong with them. They suspected that maybe the lifters were not pumping up, until they put the oil pressure gauge on and discovered it was 100 lbs.
I will find out tomorrow how the replacement pump will work. Maybe that check valve in the pump is defective and that is all the problem. I will let you know what they find out.
Thank you...
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Tom Greenleaf
Ultimate Carjunky
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Feb 18, 2009, 9:32 PM
Post #5 of 11
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Re: 94 ford aerostar wont remain running
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Techs - question:
Where is the pressure relief valve and spring for oil pressure on one of these? Oil pumps will make as much pressure as they are allowed TMK and by-pass at a certain pressure not unlike a radiator cap. I didn't think the oil pump itself was responsible for that action??
Tom
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Loren Champlain Sr
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Feb 19, 2009, 3:43 PM
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Re: 94 ford aerostar wont remain running
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The lifters, indirectly, help to open and close the valves. The lifters ride on the camshaft lobe, then a pushrod goes between the lifter and the rocker arm that actually moves the valve up and down. (actually, the rocker arm opens the valve and the valve spring tension closes the valve. Soooooo, hope I didn't put you to sleep, if the lifters are 'pumped up' (they are hydraulic) they can cause the rocker arm to open the valve, but not allow it to close by spring tension, only. If either valve on a cylinder can't close, you won't have any compression. Hope I explained that right? If the lifters weren't 'pumping up', you'd have good compression because the valves wouldn't be opening, and you'd have a lot of valve train (rocker arm) noise. Usually, from a lack of oil pressure or severe overheating. Let us know what they found. Sounds like you've got a good shop that you are dealing with, trying to get to the bottom of this.
Loren
SW Washington
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way2old
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Feb 19, 2009, 3:56 PM
Post #7 of 11
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Re: 94 ford aerostar wont remain running
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Hey Tom. The relief valve is in the pump assembly.
Being way2old is why I need help from younger minds
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Loren Champlain Sr
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Feb 19, 2009, 4:10 PM
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Re: 94 ford aerostar wont remain running
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As W20 would say, "What he said".
Loren
SW Washington
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Tom Greenleaf
Ultimate Carjunky
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Feb 20, 2009, 12:36 AM
Post #9 of 11
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Re: 94 ford aerostar wont remain running
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Got it - just didn't know where it was.
Story: These are everywhere, air compressors for shop, auto A/C and I found out that hard way that they are on your well pump at home (plumber left it out not knowing what it was doing other work) and pipes exploded when pump wouldn't quit. Never saw or heard of one fail to overpressure in a car??
T
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farnold
New User
Feb 24, 2009, 9:51 PM
Post #10 of 11
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Re: 94 ford aerostar wont remain running
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Well the shop owner decided to pull the motor out of the 94 Ford Aerostar and go through the engine again. It is still under warranty and he is not saying what the problem is. So, for now, it isn't going to cost me any money but I will have to go check on it and see what they found out. It is strange that 100 lbs of oil pressure could be the cause of the problem.
I will find out what it is and let you all know. Thank you all for your input on this one. It is strange.
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Loren Champlain Sr
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Feb 25, 2009, 3:07 PM
Post #11 of 11
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Re: 94 ford aerostar wont remain running
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Yes, please let us know what was found. Sure sounds like you and the shop owner have a lot of patience. I'm certain that he appreciates it, as well.
Loren
SW Washington
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