Oil Pressure Gauge operation

KrazyKarl · 08-02-2009, 11:17 AM

Does the oil pressure gauge in a 944S2 show oil pressure when the starter is turning over the engine but before the engine starts on its own?

I just did a headgasket and oil cooler job on my S2 and I want to make sure the engine builds oil pressure before adding fuel and spark.

John_AZ · 08-02-2009, 11:33 AM

Just like when you change your oil and filter, the oil pressure guage takes a few seconds to measure the oil pressure. No oil in the engine oil passages or filter---no reading on the guage.

Have a Mahle or OEM Porsche filter with the correct anti drain valve built in. Fram is the worst and a few others have weak oil anti drain valves.

Car must be level--remove jackstands.. Oil pickup in crankcase may suck air if not level.

Remove the DME relay to aviod washing the cylinders with gas and turn the key to start while watching the oil guage. You should see it build pressure. Not longer than 5 or 10 seconds.
OK, you see the pressure build. Put the DME relay back in and start it up.

No oil pressure? Post again and there are a couple of methods to try.

GL
John_AZ
1988 924S + 1987 924S

KrazyKarl · 08-02-2009, 11:38 AM

So it will show pressure before the engine actually starts?

I turned the engine over for about 10 seconds with the fuel pump fuse removed and the spark plugs pulled. I did not have the power steering belt on though, which apparently somehow assists with the spinning of the pump.

John_AZ · 08-02-2009, 11:56 AM

Quote:

Originally Posted by KrazyKarl

So it will show pressure before the engine actually starts?

I turned the engine over for about 10 seconds with the fuel pump fuse removed and the spark plugs pulled. I did not have the power steering belt on though, which apparently somehow assists with the spinning of the pump.

It will show pressure before the engine starts---"with the sparks plugs pulled and the fuel pump fuse removed".

By the fuel pump fuse---do you mean the DME/fuel pump relay?
By the spark plugs pulled---do you mean removed from the spark plug holes or just the wires pulled off the plugs? Be careful if you have the wires pulled off the plugs. You do not want to have the wires cause problems with the electronics.

If you have the alternator/AC belt on the oil pump is spinning.

You should get oil pressure in 10 seconds.

GL
John_AZ

KrazyKarl · 08-02-2009, 12:05 PM

Not the relay, just the fuse. The spark plugs are pulled out of the holes and the wires are out of the car. I'll put the belt on next time I try it.

John_AZ · 08-02-2009, 12:29 PM

Quote:

Originally Posted by KrazyKarl

Not the relay, just the fuse. The spark plugs are pulled out of the holes and the wires are out of the car. I'll put the belt on next time I try it.

Hi Karl,
I read the Xpost on Rennlist and you've done a great job.

I am just making sure we are taking about the same part or belt.

In the xpost you mentioned you had the DME/fuel pump relay out.

" I still wanted to make sure the engine turned over properly so I turned the ignition with the spark plugs and fuel relay out. I didn't get a reading on the oil pressure gauge after about 10 seconds. I don't remember if it comes up even before the engine starts or not until after. Can someone enlighten me? "

We want you to get it right.

The only reason the oil pump will not pump is if the crank bolt is not torqued at 150 pounds and you did not have to loosen it up to do the head. Having the PS or the alt/AC belt on makes no difference. 150 crank bolt torque does.

It may be time to try the suggestions and pour some oil down the oil filter hole.
Some even put a tube in the hole and suck oil up to the filter.

GL
John_AZ

KrazyKarl · 08-02-2009, 12:38 PM

I guess I did say relay in my other post. While I believe I turned the crank bolt counterclockwise slightly to get the engine back to TDC, it took nowhere near the 150 ft-lbs required to loosen the bolt. Thanks for the valuable input, I'm just trying to cover all my bases.

John_AZ · 08-02-2009, 03:05 PM

Hi Karl,
I just went out to the garage and removed the DME/fuel pump relay on my '88 924S.
I turned the key to start for 2-4 seconds. The oil pressure guage needle did not bounce or show oil pressure.
I turned the key to start for a second time 2-4 seconds. The oil pressure guage needle did not bounce or show oil pressure.

I replaced the DME/fuel pump relay.
I turned the key to start for 2-3 seconds. The oil pressure guage needle initially bounced 1/64 inch-hardly noticeable............., then the oil pressure guage went up normally to 4.5 bar.

I hope this helps you.

GL
John_AZ

KrazyKarl · 08-02-2009, 03:13 PM

It does, but my brain isn't working or I'm missing something. It didn't show oil pressure until it was running on its own?

John_AZ · 08-02-2009, 04:01 PM

Quote:

Originally Posted by John_AZ

Hi Karl,
I just went out to the garage and removed the DME/fuel pump relay on my '88 924S.
I turned the key to start for 2-4 seconds. The oil pressure guage needle did not bounce or show oil pressure.
I turned the key to start for a second time 2-4 seconds. The oil pressure guage needle did not bounce or show oil pressure.

I replaced the DME/fuel pump relay.
I turned the key to start for 2-3 seconds. The oil pressure guage needle initially bounced 1/64 inch-hardly noticeable............., then the oil pressure guage went up normally to 4.5 bar When the engine started.

Karl, I added "when the engine started"

GL
John_AZ

Techno Duck · Techno Duck's Garage

The relay will have nothing to do with the car building oil pressure. Whenever i change my oil i let it crank with the DME relay out and main ignition wire off the cap so the oil filter refills. It usually takes about 10-12 seconds of constant cranking for the oil pressure to come up. This is with 15w50 synthetic oil. Im not sure how much pressure you can build just cranking.. usually right as i see the needle start coming up past 2 i will stop cranking and get it ready to fire up.

I would give it another try of 10-15 seconds continuous cranking, or if not comfortable doing this do it for 5, wait a second, then continue for another 5 seconds..etc. If you still cannot build pressure, i would reprime the oil pump.

KrazyKarl · 07:07 PM

When I turn the ignition key to "on" I see the gauge move up a tic so I know the pressure sender is working. I pulled off the oil filter and filled two of the outer holes with oil excluding the one to the external cooler. After putting the filter back on I turned it over three times for 10 seconds a piece. Took the oil filter off and it was still dry but there was less oil in the holes.

I would guess it's getting pumped but not very fast since the starter doesn't turn things very fast. Should I keep filling the holes until the filter has oil in it? Or should I be filling the center hole?

cvriv.charles · 08-02-2009, 07:38 PM

The oil pressure gauge is the gauge to the left of the cluster right? numbers 1 or 0 - 5? Or is that oil level? Im kind of a noob.

Techno Duck · Techno Duck's Garage

There are a few different techniques to prime the pump. The least involved is simply filling that center hole with oil which works sometimes. The more involved techniques include spinning the engine backwards (counter clockwise from front) while pooring oil into the offset hole on the filter housing.

Another trick that has always worked for me (on various other engines) is while cranking the car, use a compressed air gun with the rubber tip and shoot 10-15 psi air (make sure you set a regulator for this or you will blow out the oil pan gasket) into the dipstick tube. You also need to plug the crankcase breather line for this method and make sure the oil cap is on. Personally if you feel cranking isnt going to work on its own, i would go straight to this method.

How long ago was the engine last run? I am surprised you are having such trouble getting pressure. Usually this is a problem after replacing the oil pump.

Quote:

Originally Posted by cvriv.charles

The oil pressure gauge is the gauge to the left of the cluster right? numbers 1 or 0 - 5? Or is that oil level? Im kind of a noob.

For the late interior cars, the oil pressure gauge is the 2nd gauge from the right. The gauge reads pressure in bars. There is an oil level indicator on i think the '86 and later engines in the oil pan. It will illuminate a oil level warning light on the dash as well as the master ! light when down a quart or so.

KrazyKarl · 08-03-2009, 06:40 AM

It has been about 8 weeks since the engine last ran. While waiting for the performance shop to open I thought of a possible reason for not getting oil pressure. With the relatively slow speed of the starter and the hole in the valve cover from the broken screw there may not be enough suction to get the oil moving. I could be completely wrong though, but I have a replacement screw now so I can try it out tonight when I get home from work.

KrazyKarl · 08-03-2009, 07:35 PM

It's alive and it has oil pressure!!

But, cylinder 1 isn't firing. I didn't smell any gas in the spark plug so I think the injector might be stuck =/

Techno Duck · Techno Duck's Garage

Try tapping the injector with a screwdriver. Sometimes that frees them up.

KrazyKarl · 08-03-2009, 08:35 PM

Tapped lightly with a magnetic screwdriver and a wrench but it didn't do it. I'll try again in the morning, maybe the fuel will work its way in and help to free things up.

John_AZ · 08-04-2009, 05:47 AM

Quote:

Originally Posted by KrazyKarl

It's alive and it has oil pressure!!
But, cylinder 1 isn't firing. I didn't smell any gas in the spark plug so I think the injector might be stuck =/

Great!

Member jmd forest would suggest using a "large" screwdriver to tap the base of the injector.
Check the harness connection to the injector. If you have a NOID light you could also test to see if the injector is getting a signal from the DME.

Anyway, Great work!

GL
John_AZ

KrazyKarl · 08-04-2009, 06:00 AM

I know it's the injector because when I use a 9V battery on the contacts I don't hear the stream of fuel like I do on the other injectors. I though it was working this morning, but when I tried to fire the car up it would immediately stall out. Felt the headers and #1 actually felt a bit warmer then the other three so I think the injector might be firing wrong causing the DME to kill the engine.