Author Topic: Can a M42 motor come out of time? (Read 23524 times)

peerless · « **Reply #45 on:** January 19, 2009, 01:02:22 PM »

Quote from: rallyegolf;64854

As for the fuel pressure. The guage maxed out. Shitty guage, but there was deffinatly pressure.

What do you mean it maxxed out? Typical F/P gauges go to like 120psi.

If it maxed out, you can't just call it a shitty gauge, You obviously have a fuel problem. If your fuel pressure is that high the car will never start. You dumping fuel into the engine. And the burning smell is probably raw fuel burning in the pipes/cat.

Just an observation, but you can't just call a gauge shitty. I could understand if it was off by a few pounds, but not maxxed out. I think you need to readdress the fuel situation.

Maybe a blown regulator. or a pinched return line.

rallyegolf · « **Reply #46 on:** January 19, 2009, 05:51:55 PM »

Quote from: peerless;64975

What do you mean it maxxed out? Typical F/P gauges go to like 120psi.

If it maxed out, you can't just call it a shitty gauge, You obviously have a fuel problem. If your fuel pressure is that high the car will never start. You dumping fuel into the engine. And the burning smell is probably raw fuel burning in the pipes/cat.

Just an observation, but you can't just call a gauge shitty. I could understand if it was off by a few pounds, but not maxxed out. I think you need to readdress the fuel situation.

Maybe a blown regulator. or a pinched return line.

I will look into this. The gauge reeds in BAR's, and I believe it went to 4 or 5 BAR, but that is before the regulator. The regulator will turn that down.
I tested the fuel line right before the rail.

KenC · « **Reply #47 on:** January 19, 2009, 06:39:55 PM »

I'm still very skeptical of your FPR... this sounds A LOT like a similar problem that I had. I was getting too much fuel on start up. Not enough compression for combustion even though it was timed correctly and had spark and fuel.

rallyegolf · « **Reply #48 on:** January 19, 2009, 07:11:02 PM »

Quote from: KenCopperwheat;64998

I'm still very skeptical of your FPR... this sounds A LOT like a similar problem that I had. I was getting too much fuel on start up. Not enough compression for combustion even though it was timed correctly and had spark and fuel.

Maybe I should just replace the FPR. Im going to do the leakdown tonight and see if Im off the charts with my compression leaks

rallyegolf · « **Reply #49 on:** January 19, 2009, 08:41:06 PM »

Well Leakdown Results:

#1 = 28% loss going out of the intake.
#2 = 28% out of intake and valve cover
#3 = 20% small intake leak.
#4 = 25% out o exhaust pipe.

The harbor freight tester is a piece of shit, but I was able to hear the air leaking trough, and by the sounds of it, I have some bad valves. No air was getting past the rings into the oil pan though.

Does this mean head rebuild? If so, how much am I looking to spend if I do the work myself?

B318M42W · « **Reply #50 on:** January 19, 2009, 11:23:10 PM »

i know this is a bit off topic... still throwing it out there: maybe your MAF is bad??? i'm thinking that if the sensor is bad, it won't send the correct amount of air going into the engine to the ECU... tells the ECU that there's no air coming in, so it sends no gas???
just a thought...

KenC · « **Reply #51 on:** January 19, 2009, 11:46:57 PM »

You did all of the readings at TDC on the compression stroke, right?

rallyegolf · « **Reply #52 on:** January 20, 2009, 09:27:52 AM »

Quote from: KenCopperwheat;65018

You did all of the readings at TDC on the compression stroke, right?

Yes, I think. I put a dow rod into the spark plug hole and turned the crank until the rod was at the highest point. That should be tdc for the piston correct.

As for the MAF being bad, I am getting fuel into the cylinders, so i'm not sure that is it. Will the car pull a code if that is bad? Also how would I test a MAF?

KenC · « **Reply #53 on:** January 20, 2009, 10:57:15 AM »

The cylinder needs to be at TDC of the compression stroke. It's also at the top during the exhaust stroke.

peerless · « **Reply #54 on:** January 20, 2009, 12:17:37 PM »

Quote from: rallyegolf;64994

I will look into this. The gauge reeds in BAR's, and I believe it went to 4 or 5 BAR, but that is before the regulator. The regulator will turn that down.
I tested the fuel line right before the rail.

3 Bar is 43psi
4 Bar is 58psi
5 Bar is 72psi

You should about 38-43 psi. This would equate to about 3 bar, not 4 or 5. You can't just guess at these things.

The higher the pressure the more fuel the injector will spray. Too much pressure is just as bad as no pressure.

Also you tested it correctly, before the regulator. The regulator functions via a spring and diaphragm. If it was working correctly then you would have correct fuel pressure every time, running or not.

rallyegolf · « **Reply #55 on:** January 20, 2009, 01:06:48 PM »

Quote from: KenCopperwheat;65042

The cylinder needs to be at TDC of the compression stroke. It's also at the top during the exhaust stroke.

What is the best way to get to TDC with the valve cover on? and will this put piston #1 at TDC or all the pistons? I was under the impression I wanted the pistons at the very top of the rotation cycle to do a leak down test. no?

this is what I found while searching the net.

Procedures
The first step is to ensure the engine is warm. Because we will be pumping air into the engine, leave all the spark plugs in except for the cylinder you're testing. As an example, let's start with a small-block Chevy, cylinder Number One. Yank the plug and turn the engine over until the piston is at top dead center (TDC). If you have balancer marks every 90 degrees, this will help. Now install the air-fitting adapter into the spark plug hole. You'll also need a breaker bar or ratchet and socket for the crank nut. Remember to double-check that your gauge reads zero before you start

rallyegolf · « **Reply #56 on:** January 20, 2009, 01:10:07 PM »

Quote from: peerless;65046

3 Bar is 43psi
4 Bar is 58psi
5 Bar is 72psi

You should about 38-43 psi. This would equate to about 3 bar, not 4 or 5. You can't just guess at these things.

The higher the pressure the more fuel the injector will spray. Too much pressure is just as bad as no pressure.

Also you tested it correctly, before the regulator. The regulator functions via a spring and diaphragm. If it was working correctly then you would have correct fuel pressure every time, running or not.

I tested the fuel right before it enters the rail. I was under the impression that the fuel going into the rail would be a higher pressure then after the FPR. I thought the FPR would keep a constant "lower" pressure then what comes out of the fuel pump. Can a fuel pump run fine, and then randomly start pumping more volume after it gets old? That doesn't sound tight to me, but I have not researched that before.

thanks again for all the suggestions guys. I really appreciate the help.

RED IS 91 · « **Reply #57 on:** January 20, 2009, 07:01:53 PM »

I believe this is the correct diagram of the fuel system .

peerless · « **Reply #58 on:** January 20, 2009, 07:38:01 PM »

You are correct the rail will have higher pressure then after the regulator. But I think you might be missing the point. Let me try to explain it a little better.

Ok you have your fuel pump. It is capable of pushing 100+psi. So in order to have a usable fuel pressure we install a pressure regulator. This regulator keeps the fuel pressure at a pre-determined pressure. In this case it is 3 bar or 43psi.

If you where to hook up the fuel pressure gauge AFTER the regulator you would find maybe 5-10psi if that.

So your pump pushes 100psi, the regulator 'Bleeds off' this pressure to the specified/designed 43psi. To prove this, hook up your pressure gauge again, and watch what happens if you pinch the return side. You will see the pressure spike to 100+psi.

Also to address what people are saying about the leak down guage. I understand your instructions say to put the cylinder at TDC. What your missing is that it has to be TDC on the compression stroke. You have a 4 stroke engine, intake stroke as the pistons goes down and sucks in air, this is when the intake valve is open, then the second stroke the piston goes upward to TDC creating the 'compression' stroke. At this point both valves are closed. Then next stroke is the 'Power' stroke as the piston pushes downward turning the crank. The last stroke is the exhuast stroke, this is where the piston again approaches TDC pushing out the exhuast gasses and the exhuast valve is open.

So as you can see if you are at TDC on the exhuast stroke you will have a exhuast valve open, and to be technically correct, the intake valve will also be on downward stroke as the exhuast valve is closing. They overlap these events to create a 'vacuum' or 'Draft' effect. As the exhuast is flowing out the exhuast valve it will actually help pull in the following intake charge. Kinda like opening two windows in the house to get a 'draft' or 'breeze'. The velocity of one helps pull the other.

So in the end, if you did your leakdown on TDC exhuast you would hear air coming out of the intake and exhuast valves.

I think a more conclusive test here would have been a simple compression test. Typically in diagnosing something of this nature a compression test is done first. After it is determined that a loss of compression is present, THEN you do a leak down to pin point it.

Some diagrams to help you picture things better;
http://www.aa1car.com/library/fuel_pump_diagnose.htm

Here is a video of the 4 cycle process.
http://www.youtube.com/watch?v=-8cXXjsRg70&feature=related

And finally we have a diagram of valve timing. Its for a different application but you can clearly see the overlap of the intake and exhuast at TDC on the exhuast stroke.

rallyegolf · « **Reply #59 on:** January 20, 2009, 09:59:10 PM »

Thank you guys for clearing that up for me. I was obviously doing the leak down test incorrect. I guess to do it the right way, I need to find out how I figure out TDC on the compression stroke of each cylinder.

If I get the motor to "true" TDC, then is that the compression stroke on piston #1? After that, I just figure out the firing order and turn the crank to the next piston at TDC that is the next to fire. Does that make sense?