Is it possible / feasible to increase the compression in an engine? I took my 1990 BroncoII to a shop today and learned that two of the six cylinders have no compression. They say the engine needs replacing which would run about $3500. Naturally I'm not going to do that for that cost. However, if there is something I can do to improve the engine, I'd like to know. Would using a higher octane gas give me more power from the four working cylinders or would that not matter so much? Alternatively, if anyone knows of an available working engine in upstate New York I'd consider swapping it in.
If 2 of the 6 have no compression and they are next to each other, then you probably have a bad head gasket (could be a cracked head or block too, hard to say for sure). Short of replacing the gasket, there is nothing you can do to patch it up.
I'd bet the head is cracked, at the very least. I found this group after buying the vehicle and heard some opinions that this engine tends to get cracked heads. Putting all the evidence and opinions together, that seems to be a reasonable conclusion.
Well, it could be greater than zero but still insignificant. Sometimes the engine runs fine, and other times it is really rough and has no power. I mean, little power - enough to move on level ground, acceleration is slow and inclines give me trouble, highway speeds are manageable only on level ground or declines. When it is acting up, it will either idle at normal speed but be rough and the stick (manual trans.) shakes or it will idle around 500 rpms and sometimes stall silently. The problem has been more frequent lately. The shop said I had no compression. They probably meant "no compression worth mentioning" :-).
I was hoping I could do something simple to improve the situation. It's unfortunate, since I bought this BII for the winter and have put too much money in it already. I'll keep running the cheap(er) gas, then, and wait to get stranded. (unless someone can provide an inexpensive replacement engine)
I was kind of toying with the idea of converting it to a V-4, but I'm sure that would require pulling the engine out (which I can't do) and probably impossible (or just impractical) adjustments to the timing.
I don't know that I would bet on a cracked head, blown gasket, burned valve or other mechanical failuer of the cylinder or head. I say this because you decribe the problem as more or less inconsistent as in "when it is acting up". That suggest to me that you may have low compression in 1, 2 or more cylinders that needs to be addressed but, you at least have other problems related to fuel delivery, ignition or emission control problems. As far as converting it to anything other than what it is, that will be a more expensive repair than just replacing the engine or repairing your engine. You need to get the engine to someone you trust who is capable of giving you a complete rundown and evaluation of the problems you face with this vehicle. You should be aware that your Bronco II may be worth far more in parts that what it will cost to repair. You need to figure out id you are in love or in heat on this one.
I guess it is a definition of 'no compression'. Kind of like the definition of what "IS is". I would suspect that even with the piston hole or burnt valve, there should be some kind of reading even if it is only 5 lbs.
: > Yeah what Chris said. :) : >
: > But what about this -no- compression thing? I've never ran across : > that yet, is -no- and exageration? : >
That's kinda what I was thinking. The mechanic was just being dramatic instead of specific? I don't know whether zero compression reading is possible. :/ ...but want to know. :)
That and the high price.... does a guy want a "dramatic rather than specific" mechanic charging you money? ;)
More or less. Now it's mostly "more" and very little "less". It started about a month ago. Cruising down the highway, the engine just started shaking for no reason and had little power. I turned around and it drove fine almost the entire way back. My girlfriend's dad and I replaced the spark plugs, distributor cap and rotor since they were old and worn. It ran great, better than when I got it, for two weeks (about 1200 miles). Then it started intermittently yielding the same symptons though not quite as bad. I poured injector cleaner in the gas tank. The guy at a local parts shop didn't even blink as he said "fuel filter" when I described the problem to him. I replaced that, still with no improvement. The owner before me had replaced the gas tank and sending unit, within the past 3 years / 40K miles.
Over the past week, however, the condition has changed from "sometimes failing" to "occasionally working". For example, yesterday I drove about 80 miles. For about 5-8 of them the engine ran smooth and had power. In addition to the amount of time the engine isn't running right, I now have to practicaly floor the accelerator to move, and starting in second gear is impossible. With the ground being mostly level or a slight downgrade, I was able to take the expressway home at
55 MPH in 3rd gear at 4200 RPMs and the accellerator almost on the floor. This morning, heading to work, the engine ran well, while in second gear, for about 10 seconds as I drove out of the apartment complex.
Given this rate of decline, I'm not confident it will be self-propelled for much longer. (unless you have a bright idea, of course :-))
Before I took it in to the shop, several other people also suggested to me that I have some sort of fuel delivery problem. I was told it could be a worn injector, or electrical connection problems with the computer or a sensor.
Do you still doubt gasket or head failure with the additional information above? Could the fact that the fuel guage is stuck on empty be a real problem? The previous owner said it has been like that for a long time, and I don't mind using the trip odometer as a substitute. Are there tests I can do myself to confirm or rule out these possibilities? I am not very experienced, yet, but I want to learn how to do as much as possible for myself. Class at the local community college starts in a month and a half :-).
I'll talk to a friend of mine and see where (if) he is now working as a mechanic and see if he'll look it over. The shop I took it to on Monday said I basically need a new engine, which is in the ballpark of $3500. For that price (and add in labor and tax) I could get another used 4x4 in much better condition.
The funniest part of all this is the "Check Engine" light never came on, until I was leaving the shop after having it checked. Now it comes and goes. I might pull the code just for kicks. I know exactly how to do it with a GM (Oldsmobile). Is Ford the same? Find the connector, short two of the pins on the end and count the blinks of the light?
Yeah, I think you are right about this. I bought the vehicle this year to use during the winter season. It has 4WD and my F-150 doesn't. Living about a mile from Lake Ontario and driving 15-20 miles to work every day, I'll see plenty of snow. Unfortunately I've already spent around $5K (USD) on it and winter is only just peeking around the corner. I didn't want to drive my truck because of the 2WD and also the salt that is used on the roads. However, unless I get an astronomically good price for the BII I can't buy another vehicle this year and will have to use the pickup. For (not-so-)future reference, where are some good places to sell used parts?
I agree that his problem probably isn't a cracked head or head gasket or burned valve. But, a sticking valve or two could explain the intermittent compression symptom. I'd pull the valve covers and see if they are all closing properly and consistently. Dave
But first what about the compression test being re-performed by the OP and his mechanic buddy? It's easy as pie to goof up that test when it ain't your money on the line. ;) Get the numbers this time.
Where would that be located? The index of the Helm manual makes no mention of such. (I've noticed, though, that the index leaves out a lot of specific parts assuming the reader knows what larger component to look for it on) The section on "Fuel Charging and Controls" mentions a Manifold Absolute Pressure (MAP) sensor in the description ans says that sensor affects the fuel/air mixture, but I don't see it mentioned in any subsection or any diagram.
It's nice when people at least agree on what could be wrong. :-)
I looked in the Helm manual, and I don't think I should even try taking the covers off by myself.
Yeah? How is the test performed? Could sensors, ignition, and/or fuel delivery/injectors affect the outcome of a compression test?
I'll ask for them.
On the plus side, the engine kicked in and worked part way to work this morning and about halfway home this evening. Much better than the previous couple days where it only barely hinted at working right. The past couple days have been "warm" (above freezing, almost nice) and a light dusting of snow was falling on the way home this evening. Perhaps the drop in temperature improves the condition of whatever is failling? (if it is a sticky valve, maybe the cold decreases the stickiness like with chewing gum)
I'm so far out of the loop with this new fangled stuff I didn't know covers needed removing. :/
With a mechanical pressure gauge with a one-way-valve (in!:) and that captures the pressure made by the cylinder. The service manual should have the complete method of how to perform the test.
All the spark plugs are removed (and the carb propped open;) and the starter is used to crank over the engine until the pressure gauge reads as high as it's going to read.
Sometimes the readings are re-taken after the first "dry" run- through but this time after sqirting a little oil in the cylinders. Depending on the difference (or lack there of;) of the dry and wet readings tells you about the condition of the rings (directly) and valves/head gasket (indirectly).
I meant when you and your buddy re-do the compression test. But if you can get them, it wouldn't hurt to get the extra information.
On Fri, 12 Dec 2003 03:33:55 +0000, Derrick 'dman' Hudson rearranged some electrons to form:
If the enginer controls are "speed density" there is no MAF... the computer calculates air volume based on manifold pressure and engine speed. I don't know when they made the switch on Broncos. If there is a MAF it will be in the air intake path somewhere...it's usually a metal venturi with a couple of little teeny wires across the air flow path.
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