Changed to thicker oil - now no start

[exitwound]

I've been having oil pressure problems lately. Here's the scenario:

- Low pressure at idle when warm, normal pressure during rev/cold engine.
- Power steering crank pulley was shot. got a new one. Torqued to 155ftlbs, same thing. the torquing of the crank bolt doesnt' seem to be the problem.
- Took out and cleaned the OPRV (3piece old style). As far as I see, it's not sticking. In fact, the plunger falls right out of the block smooth and silent if the spring isn't holding it in.
- Changed the oil from 10W40 to 20W50 to thicken it up. Put in ~6quarts. Started car, had little oil pressure. Slowly it built to 4.5 bars. Took the car around the block, no problems.
- Today, the car won't start. Starter cranks and cranks and cranks, but there's very little sputtering and no start. I charge the battery up, and the same thing. No matter how much over "cold of winter morning" the engine is, it won't even give me a sign that it's trying to fire.

The only thing different is the weather. went from 55F to 34F here in PA but the starter is operating fine.

Checked for any oil leaks and found none. Bypassed the idle control valve - no effect. Bypassed the DME Relay - no effect. TPS valve seems okay. Air filter is clean (looked for squirrel nests). Only thing I've done is removed the air intake to get to the fans to get to the crank bolt. But it all worked after I put it together. Car still won't star tonight.

During cranking, I have 3bars of pressuring showing, a proper torque bounce up to 500rpm, and all dash lights and dome light work properly.

What could I have done?? Why won't it start?

Going nuts,
Pennsylvania.

[JonA]

I had a problem with an engine swap in a Nissan where the starter wasn't giving the minimum rpm and it wouldn't start. Pushed it down the road and it started right up. Jump start or put thinner oil back in and see what happens.
There is a current thread on the board about rebuilding starters that may be worth a look.

Good luck,
Jon

[jpk]

What's going on is probably not related to the change in oil. Start with the basics - check for spark and fuel. Sounds like the DME is getting power (you say the tach is reading 500 rpm), but maybe the second coil in the DME relay is bad and the fuel pump isn't getting any power. The tach reading also indicates the speed sensor is OK, but if the refrence sensor is bad, the ignition timing will be way off.

[exitwound]

I've been reading around and most threads have said that if there's a tach bounce then both the speed AND reference sensors, as well as the dme have to be good. The fuel pump is powered and running with the key on as well as when the DME relay is jumped with a 3-prong jumper (it's an audible flow of fuel from the pump to the engine).

How do you check for spark if you dont' have a helper buddy? This is my main issue as i have no one willing or able to help me test due to the cold. (Whiners.)

[emoore924]

Did you load test your battery?

[exitwound]

11/20/08 Update

• Throttle position sensor operates perfectly, all three settings.
• Air flow meter voltage is operating perfectly, smooth as the door is open.

11/22/08 Update

• Noid light confirms all four injectors are getting a pulse as the engine is cranking.
• Ignition coil sending spark.
• All four plug wires are sparking.
• Fuel pressure at the rail is 38psi with the DME relay removed and jumped.
• Fuel pressure at the rail is 38psi with the DME relay installed.
• Fuel Pressure dampener and regulator have no fuel in the vacuum lines.
• Pulled the fuel rail. tips of the injectors are wet.
• Replaced the reference and speed sensors with ones that are known to work from another 86 944. No change.

The only thing I can see that might be an issue, other than what was posted above, is that the fuel pressure in the rail drops to zero after about 1 minute when the car is off. Shouldn't the rail retain the pressure for quite some time after? It's a new fuel pump, with new valve, new fuel pressure regulator, but the dampener was never replaced.

At this point, I believe I have fuel, spark, and air. The only possible causes are lack of proper timing due to the reference & speed sensors being old, and the quickly falling pressure from the fuel rail when the engine is off.

Any thoughts?

[JonA]

As my earlier post mentioned, I believe the reference sensor has to see a minimum rpm when cranking to send a proper signal. Your thick oil may have slowed cranking to under that threshold. If you have a hill nearby and a standard tranny give her a little push and see if it will jump start.
The caveat here is my adventure was with a Maxima. We put a junkyard engine in and the starter turned out to be wrong with not enough rpm. I spent weeks with schematics and my multimeter and $200 worth of unneeded parts. I'm pretty stupid but I don't give up. That was two years ago but even today every time I pop the hood on one of the cars someone in the family always reminds me to "check the starter, Dad".
Good luck,
Jon

[earlr85944]

you looked for squirrel nests, cool: but did you look for squirrels?

[exitwound]

But as far as I can tell, the engine is not cranking any slower than it was with the thinner oil. And the car started when the oil was first changed, after sitting for a day and a half prior without start.

[zedsn]

Maybe you might want to do a compression check? Doubt it but maybe the cold weather has dropped your compression some and causing it not to start?

[exitwound]

Just got it to start. I swapped out the reference and speed sensors from another 944 last night but without any luck. Today I did the same thing, and this time I got it to work, but not without some trouble. Per another user, I held the throttle open all the way (WOT) and the car seemed to want to start but shuddered and stalled out without the gas. After a little bit, the car ran fine. I swapped my own sensors back in, and now the car starts fine. I honestly have no idea what the problem is though.

[ihuntsum]

I think I am having a similiar issue with my car. It killed about a week ago and I cleaned the sensor connectors with WD-40 and it started right up. Friday it stranded me again with no spark. I have tried cleaning the connectors again with WD-40 (no electrical cleaner on hand) to no avail. Damn I wish I had an ocilloscope. Trying to get a hold of some different sensors. If this issues continues I am going to hard wire in the sensors. If this is to be my daily driver I have to make it more dependable.

[exitwound]

Yes I know the feeling. If it's not one thing, it's another. And it's never obvious either. Cut my hands up pretty bad working on the sensors. Careful not to drop the bolt otherwise it goes into the bell housing?! Nonsense sometimes, I tell ya.

[JonA]

Put in some winter weight oil...........

Jon

[Dean924s]

My bet is you flooded it and washed the cylinders. You then had a flooded car with lower than normal compression.. . . and no matter what you do it will not start. Some times pulling the FP fuse and cranking with WOT will get it to fire.

The problem is that in the cylinders fuel will not evaporate it will just sit there. I am finding this to be more of a problem with the low VOC fuels. I dont know if anyone of you have noticed that the new gas does not evaporate like the old stuff use to. Even if you wait a day you will still have a flooded car. If it gets to bad you will wash all the lubricant off the rings and the cylinder walls as well as the sides of the midlands. Every time you try to star it The car keeps trying to add fuel. You will never get ignition.


Sorry I missed this thread when you were asking for help. If it happens again remove the plugs and inspect for flooding/wet plugs. Having new ones on the shelf even if they are cheep ones is a huge help here. Anyway, then pull the FP relay and then spin the motor over for a few moments with the plugs out. Then put a squirt of oil in each cylinder. Not WD40!!! A little motor oil or atf is good. then crank the motor over again with the plugs out and the fuel off.

You can try to start the car now but I would recommend that i you have the time let it sit for a couple of hours and if possible hit the cylinders with compressed air. If you don't have that dust-off works. The idea is to get every last trace of fuel out and get the rings and cylinder walls lubricated again.

Oh Ya did I mention new plugs? This make the process much easier. I try to keep a stair set around at all times. IF you dont have a set you will have to clean up the set you have. This can be a SOB as flooded plugs can get this weird black glaze on them and they just dont seem to want to fire properly unless you get it all off.

Now that I have babbled on way to long you may want to investigate what / how the car flooded. You may want to test the DME temp sensor for starters.

I have had this happen to several of my car over the years. Once a 944 floods it almost always has to be manually un flooded.

[exitwound]

Thanks for the writeup. Babbling can be a good thing sometimes.

New DME Temp sensor, btw. I'll have to investigate this a little more, see what The Google has to say about flooding injectors. I've never come across that before.

Interesting....thanks!