View Full Version : How to diagnose SC?

02-28-2005, 04:14 PM
this is the deal,

I was driving my 89 SC (5SPD) the other day cruiseing at about 70 MPH when the engine started loosing power. No loud sounds or anything like that, no smoke, etc....Will run, but barely. No power. Towed it to ford since my house is 40 Miles away.

The ford mechanic was pitiful! Told me at first clogged CATS, then he said the engine is toast, likely the crank is twisted and is out of time. WHAT??????

I believe the engine is fine, no blown head gasket, no sheared off Harmonic balancer. I am guessing it is a timing chain or it could be the gasket that connect the Super charger to the intake manifold. Any other ideas.?

02-28-2005, 04:55 PM
could be clogged fuel filter. pull it out and see if you can blow threw it

02-28-2005, 05:12 PM
I just put a new one in less than a week ago, performed major tuneup at the time.

02-28-2005, 05:29 PM
I was thinking, if the crankshaft is cracked, would there not be some serious banging and metal grinding sounds? I think the Ford Mechanic is full of crap!

Does a 3.8 Liter with 120 K miles ever jump a tooth on the timing gear?

The SC to intake manifold gasket deteriorate, has anyone had that happen to them? Could this be a reason why it is running rough?

02-28-2005, 09:22 PM
Does a 3.8 Liter with 120 K miles ever jump a tooth on the timing gear?

If it's the original it sure could.

03-01-2005, 04:24 AM
If for some reason your charging system went south and the engine was running off the battery and running it down, the engine will first begin to run like c**p and then die along with everything electrical. So, be sure you have a fully charged battery before you do anything. Next would be to understand that you did not hear any mechanical noises from the engine as you began to loose power, so that would most likely rule out anything mechanical inside the engine. Get your car to someone who can troubleshoot it correctly. From what you said in your post about the guy taking guesses, and the fact his guesses are wildly extreme, should tell you that either he is joking or could care less about how much it will cost you. Best to CYOA!

03-01-2005, 08:35 AM
I'd hafta agree with some of the other posts. Sounds like either fuel or electrical, PROBABLY. I'm not saying that it can't be mechanical, because it could. A lot of times tho, a timing chain needs some event to happen to make it jump.They are pretty stout. Usually it's a big backfire, or other malfunction causing quick rotational reversal that does in the chain/timing. When your just cruising along, then you get that,blah-h-h-h deal where it just dies, I usually look at electrical first, a shorted wire, or loose connection. Could also be fuel, but thats not always so instant, usually a slow deterioration of performance, marked first by stalling and rough running.
First I'd get that car away from the dealer.Sounds like they threw you to some kid that didn't have a clue, and was just guessing. Twisted crank? Yeah, right. That crank is forged, and you don't have 400HP either. Twisted sister acting as twisted mechanic. All the dealer is going to do is bill you to death before they find the problem.If thats all thats available, ask for the oldest, wisest mechanic on the line to take a look at it. Make sure you talk to the service manager about the "service" you got, and the "diagnosis" you got.Get a written estimate of exactly whats wrong with it, then get it out of there. Personally, I would not reward them with my money. Find the most knowledgable mechanic in your area. Maybe someone here has a suggestion for your area. Proper diagnosis is a slow elimination of causes, starting with the basics, not jumping to the crank or cats (clogged up in 10 miles,wow, how 'bout that-). It can run $200 to find out, but thats better than $500, and they still don't know! Do NOT tell the outside mechanic what the dealer said, just watch how he does his diagnosing, and learn. Let him come to his own conclusion.When you get the REAL problem fixed, take it back and show the same service manager what it cost you to have it diagnosed and fixed correctly.Probably less than 1/2 of what their estimate was. When I get crappy service from the people who are SUPPOSED to know about my product, and charge like they can do no wrong, I do not hesitate to berate them for their service, or remind them, that I am perfectly capable of writing to THEIR boss, Ford Motor Co. about my "dealer experience". If they look like a-holes then they deserve to be called that. I've had this same kind of dealer experience, and I have also had excellent dealer service. There is a huge difference between the two!
Also, study exactly how the air is routed thru your engine, so you understand it better. There is NO direct "supercharger to manifold gasket" like you are asking about.It IS complicated, and not as easy as a "normal" car. There is a lot more plumbing, but you want horsepower, right? I don't have time to explain it all to you, but you need to understand how it works. Study Manuals, so you know.There are several points where you could have either a vacumn or a pressure(boost)leak, but none of them will cause a car to just completely die like you described. Eliminate the simple things first, starting with electrical and fuel. As in the battery, fuses, and wires. Spark and timing. Fuel Pressure. Etc. Etc...... Good Luck!

03-01-2005, 11:11 AM

thanks for all of the replies.

I am quite sure that I can fix anything that is wrong with my car. I have rebuilt several engines, transmissions, and am quite good at trouble shooting.

The reason why I even took it to the dealer was it broke down 40 miles from my house. I spoke with the mechanic today and he told me he did not put it on any diagnostic equipment. He did tell me again that it was mechanical, the crankshaft can twist (Forged Steel?????? :mad: ) or the timing chain has slipped a gear.

My goal is to get it in on a dolly and tow it to the closest military base where I can get it up on a lift.

This is my plan,

1. check for fuel pressure

2. check DIS

3. Check for SC to intake manifold gasket, there is such a thing, oval at the back of the engine. Since this is my first SC engine, I don't know the names of specific parts very well, but I do understand the operation and how the plumbing works.

4. If they all check out, I will pull of the front timing cover, this is my last resort because I know it can be a bear to get the oil pan off.

03-01-2005, 11:33 AM
Before you put any $ into fixes, see if the computer can give you some hints. If you don't know how to do this, do a search on pulling codes. It can be done with a paper clip, pencil and note pad.
In your case, I wouldn't be at all surprised if you had a DIS related stored code.

XR7 Dave
03-01-2005, 11:45 AM
1) You are headed on the right path. Basic diagnosis will find the problem if you follow a logical path.

2) The timing chain cannot jump a tooth. It is tensioned and simply cannot jump teeth.

3) The crankshaft will not twist. It may break, but that would mean no-workie anymore!

4) Most likely problems are DIS, fuel pressure, or broken balancer.

The balancer does not have to fall off or wobble to fail. It can simply spin on the hub causing very retarded timing which would act like clogged cats or jumped timing. The best way to check the balancer is to use a piston stop to determine TDC and compare it to the marks on the balancer.

03-01-2005, 12:06 PM
Yes you can jump one. Tensioner works if the inserts are there. There plastic and get britle and break off. And not just fords, I've seen it on pontiacs chevies. I used to own an auto exhaust shop. And Yes cranks twist too. Deflexsion if what they call it. They twist before they break as well.

03-03-2005, 01:14 PM
This is waht I have come up with.

1. Harmonic Balancer is fine....looks great, I wonder if it has been replaced before??????

2. Crank seems to be okay for now, no excesive play, or clunkiness, etc.

I am going to replace the Crankshaft Position Sensor. Check the fuel pressure. The Mechanic at the hobby shop said he will put it on whatever system they have to diagnose it.

then after that, if things don't work, I will pull off the front cover and oil pan to look at the internals.

03-03-2005, 09:48 PM
Clean your mass air flow sensor with a q-tip and some rubbing alcohol. A small chunk of crap in there will turn everything sour.

Just my $.02

Dylan Roth
St. Cloud, MN

03-14-2005, 08:30 AM
As I suspected it was a Fuel pump.

I tested the pressure at the schrader (SP?) valve and it was less than 2 lbs. I also connected up the diagnostics and I believe it was code 87, fuel pump circuit.

Anyhow, I replaced the pump, and it fired right up! It works great! I am going to the Ford Dealership today and ask for my diagnostic fees back. I should ask them for a job as well! :)

03-15-2005, 11:06 AM
Got my money back from the Ford dealer.....didn't ask for a job though. Maybe next time. :)