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Singing the no oil pressure blues

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Old Jun 25th, 2021, 21:03   #1
142 Guy
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Default Singing the no oil pressure blues

I was out driving around a couple of evenings ago. I came up on a red light and had to do a firm stop and I noticed that the low oil pressure warning light on my electronic oil pressure gauge flickered on. Its programmed to do this if the pressure drops below 10 psi. Pulling away after the light changed I noticed that my pressure was lower than normal - about 30 - 35 psi @ 2500 RPM. The low pressure warning flickered again at the next stop light so I pulled over, got out and checked for oil leaks (I had checked levels a couple of days ago so I knew that was good), found none so I carefully drove home watching the pressure gauge to keep it up around 30 psi. The mechanical oil pressure switch never activated during this event so I never reached 0 pressure. Prior to the oil pressure warning light coming on that first time everything had been just fine. There were no strange mechanical noises before or after the warning light flickered.

This morning I double checked the sump oil level and it was at its normal level. On the off chance that the electronic gauge / sensor may have gone out of calibration, I disconnected the mechanical pressure switch and hooked up a mechanical oil pressure gauge so I could carry out a test to determine whether the electronic gauge was the problem. In order to hook up the temporary 'plumbing', I had to remove the oil filter to get at the fittings on the side of the block. Almost no oil drained out of the filter as I pulled it off which is not normal. After installing the fittings for the mechanical gauge I installed a new filter and then proceeded to carry out a cranking pressure test with the coil and injector fuses pulled so it would not start. I did 3 crank tests of about 5-6 seconds each and I am now getting absolutely no oil pressure on either the electronic gauge or the temporary mechanical gauge. The tube to the temporary mechanical gauge is translucent nylon and I could see that there was no oil flowing in the tube.

So, I have now gone to zero oil pressure which leads me to the following possibilities:

- one or both of the rubber rings that seal the oil delivery pipe have moved / fallen right out (I would have thought that I would still gets some oil flow to the galleries when cranking),

- the oil pump has had a drive end failure (I have that IPD re enforcing ring on the oil pump drive)

- the pump pressure relief mechanism has failed open (I have the IPD high pressure spring)

- the little tab on the end of the oil pump / distributor drive shaft that engages the oil pump has sheared right off (I would have expected this would have resulted in complete loss of oil pressure while driving).

Have I missed anything? I will add that the engine had a complete rebuild about 7 years ago and only has about 6000 km since the rebuild. Oil pressure prior to this event was just fine.

As I recall, I think the oil pump / distributor drive shaft can be removed and checked once the distributor is removed so I should be able to check that fairly easily (getting it back in to the pump with the IPD re enforcing ring will be a treat. However, if it did shear off I expect that the pump has to come off to get at the broken piece that will be stuck in the end of the pump drive. Everything else looks like removing the sump is a requirement. From the service manual, it appears that I can remove the sump with the engine in the car. This does require having the front of the car raised up, lifting the front of the engine and then dropping the front cross member a bit to get access. Once the oil pan is off I presume that access to R&R the pump is straightforward?

The sump gasket will have to be replaced. Any comments on Reintz / Felpro / Mahle / AJUSA / Elring? I am pretty sure the existing gasket is an Elring cork gasket which has weeped from day one so something that seals better would be nice. I have limited garage space so I want to get this repair turned around as fast as possible. In the event that the oil pump / pressure relief is buggered I want to have a replacement on hand so that the car is not taking up space for a couple of weeks while I wait for parts. It looks like the Melling M91 pump is the only replacement option?

If the problem was the seal rings on the oil delivery pipe, any words of wisdom on re installing those puppies so that they don't pop out again? Any other words of wisdom on possible causes or tricks in doing the repair?
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Old Jun 26th, 2021, 07:15   #2
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Never had a failure myself so really cant guess what would be the normal culprit. I suppose its check the pump and pipe first. I think they are more likely than a drive failure. I put a uprated pump from KG trimning in my Amazon engine, not sure if that is good or bad. Gaskets not sure either, just used what was supplied and never had a leak on the sump.
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Old Jun 26th, 2021, 15:41   #3
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Do you know what the brand is for the uprated pump from KG? In addition to the Melling pump I discovered that there is a Volvo OEM pump and one from MTC. I have tried the MTC brand engine mounts and based upon that experience I don't think I will be trying the MTC oil pump.

IPD in the US sells a heavy duty pump; but, it is just a regular pump (I think it is an MTC) with a high pressure relief spring and there little re enforcing collar.
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Old Jun 26th, 2021, 15:43   #4
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Quote:
Originally Posted by 142 Guy View Post
Do you know what the brand is for the uprated pump from KG? In addition to the Melling pump I discovered that there is a Volvo OEM pump and one from MTC. I have tried the MTC brand engine mounts and based upon that experience I don't think I will be trying the MTC oil pump.

IPD in the US sells a heavy duty pump; but, it is just a regular pump (I think it is an MTC) with a high pressure relief spring and there little re enforcing collar.
No sorry. I assume the KG's one is the same with a heavier spring.
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Old Jun 27th, 2021, 17:57   #5
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I pulled the distributor drive gear off yesterday afternoon. The drive gear shaft is fine and the top of the oil pump where the drive gear shaft engages the pump looks to be fine (as much of it as you can see looking down through the distributor drive hole). So it looks like the pump must have failed or the connecting pipe gaskets failed or the pipe fractured.
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Old Jul 5th, 2021, 09:21   #6
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I have known the filter on the bottom of the pump to get clogged, one of the rubber sealing rings on the pipe from the pump to the block to 'push out' Both ways it's sump off and i would remove the pump check and replace the rubber rings on the pipe. These were pretty rear but did happen on a few occasions.
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Old Jul 27th, 2021, 04:15   #7
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Time for an update.

First off, need to vent! The Volvo 140 service manual is slightly out to lunch in the section that covers replacing the sump gasket without removal of the engine. In step 4, the manual says:
Remove the rear bolts on the front axle member and screw on instead two auxiliary bolts (UNC 1/2-13x114). Remove the front bolts for the front axle member. Lower and remove the jack so that the front axle member is suspended in the two auxiliary bolts.

The 1/2-13x114 was confusing. I assumed that it was a typo that meant UNC 1/2-13x1 1/4. so I dutifully picked up a pair of 1 1/4 long bolts for the job. After doing this, I looked at the cross member with the car up in the air and thought "with the front bolts removed and a couple of 1 1/4 bolts holding the back of the cross member in place the cross member is going to drop in front and pivot up at the back. How is that going to make additional clearance to get the oil pan off". However, I figured perhaps that Volvo knows something I don't and a miracle occurs. Nope. No miracle occurred. With the short little bolts the cross member pivots up at the back reducing clearance as you lower the jack under the cross member. I put everything more or less back in place and looked at it and then went out and bought four UNC 1/2 13x 4 1/2" bolts. I replaced all the cross member bolts with the 4 1/2" bolts and then used the jack to lower the cross member straight down with the 4 bolts keeping everything lined up. That provided plenty of clearance to remove the pan. The other details that Volvo omitted were that I needed to remove 1 of the bolts on both the pitman arm mount and the steering box mount because the inside edge of both upper front A arm pivots was just catching on the bolt. I also needed to disconnect the sway bar to allow the brake lines to move as the cross member was dropping. If you are doing this, watch the brake lines very carefully. Depending on how far the front of the car is jacked up and the length of those four bolts suspending the cross member, the crossmember and by extension the calipers may drop enough that they rip the brake lines right out of the bulk head mounts. Mine were definitely tight.

In retrospect, I am wondering if 1/2-13x114 meant a 1/2 inch, 13 thread per inch bolt that was 114 mm long. 114 mm would be about 4 1/2 inches. Nothing like mixing imperial and metric measurements together for confusion.

The attachments show the fixture I fabricated from some scrap 2x4s and some hooks and chain to replace Volvo SVO 2727 which holds the engine up once you have disconnected the front engine mounts and lowered the cross member. Volvo just uses a rather small bolt at the top of the timing to suspend the engine. On the later B20 heads there is a mungo bolt hole at the top of the head on the right so I used that as the primary support with the timing cover bolt used to keep the engine level.


The rest of the operation went pretty much without a hitch, ignoring the 3 week delay in getting the pan gasket from Rock Auto after Fed Ex lost the first one. As to the cause of the low and then no oil pressure (during subsequent testing), that is a mystery. When I went to remove the oil pump and the feed line to the block, both rubber seals on the feed pipe were firmly in place. In fact, the B20 feed pipe has a ring on it on each end which backs the seals when the pipe is inserted in the pump and the block. You can't even see the seals when the pipe is inserted so I am thinking that there is pretty much zero possibility that the seals would ever pop out under pressure. When I unbolted the pump I had to give a very firm yank to get the feed pipe out of the block (same at the pump end). It definitely wasn't coming out on its own.

I installed the new pump and buttoned everything up with some new 5W50 oil. I modified a 12" flat blade screwdriver to allow it to be inserted down into the distributor drive hole and allow me to turn the pump by hand. I did a couple of CCW turns by hand and then the resistance increased as oil began to flow. I gave a few more turns and I could see oil flowing into the hole for the distributor drive gear (supply to the drive bearing) and oil flowing in the nylon line to the test oil gauge. I installed the distributor drive gear and my cam sensor carefully following the alignment marks I had painted on the distributor hole so I would not have to go through a timing reset exercise. With the cam sensor in I reconnected the battery and did a test crank of the engine. A few seconds cranking gave about 30 -35 psi on both the dash and test gauge. The battery was a little low after sitting for 4+ weeks so cranking was a bit slow. I disconnected the test gauge and reinstalled the oil pressure switch, reinstalled all the fuses that I removed for the initial pressure check and then fired up the engine. Start up was quick and the oil pressure rose to around 55 psi very quickly. I let the engine run to check for leaks and allow the coolant temperature to come up to around 90 C for a few minutes. With the engine idling at around 850 RPM oil pressure was rock steady at 55 psi even after the temperature had been up above 90 C for about 10 minutes. That is a definite improvement over the old pump as pressure would sag to around 30 - 35 psi at idle when hot.

I pulled apart the old pump to see if I could spot the problems for my low / no oil pressure. I was expecting to find a broken oil pressure relief spring; but, the check valve was intact. I looked to see if there were any objects holding the ball valve open; but, didn't spot anything. According to the service manual the tolerance on the tooth flank clearance is 0.006 - 0.014" and mine measured out at 0.013" on some of the teeth pairs; but, not all. Some of teeth pairs were tighter. The end float on the driven gear was between 0.002" (loose) and 0.003" (tight). The service limit is 0.004" so mine was within limits. The pump measurements were all within; but, close to the upper limit of the service tolerances. The pump wear probably lines up with the lowish oil pressures that I was getting at hot idle; but, I didn't see anything that would be responsible for the sudden drop in oil pressure that I experienced or the fact that during the test after getting the car home I was not able to generate any pressure of flow at all.

Out of curiosity I reassembled the old pump and then inserted the pump into a small pan that I filled with old oil. I rotated the pump drive gear and after a few rotations was able to generate flow through the pump. That is not a test of pressure; but, it is an indication that the pump could generate flow. Why I got the no flow results in my test remains a mystery. However, the new pump definitely does work better at idle than the old pump.
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Last edited by 142 Guy; Jul 27th, 2021 at 04:19.
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