TS3.8L 96 oil pressure/fuel pump switch

[WelmoedJ]

From the factory manual I understand that the oil pressure switch also serves the fuel pressure system.
In another thread I noticed low oil pressure could be caused by either a faulty switch, a failing oil pump, the wrong (FRAM) oil filter or a combination of this.

My Trans Sport 3.8L V6 (L27 series) has run now over 250k Kms so some of the issues could be related to the "mileage" of this car.
For some time I have a low pressure on the gauge, which drops to the white line above the red zone while idling and approx at the second white line above the red zone while driving.

Regarding the mileage I at first assumed the oil pump going out.
But now that the fuel pump starts humming noticeably I think it also could be the oil sender as this unit also is connected (power?) to the fuel pump.
This car is equiped with a FRAM oil filter, of which I now understand, is not the best filter for this car.

It may as well be both, but I like to get some advice as where to start my investigation.
I do have a possibility to check oil pressure, but I'm not sure if I can do that after removing the oil/fuel pressure switch.
Should I have a bad oil/fuel pressure switch I can go for an original, or as mentioned in another thread go for one of an Olds, which is said to be better. However to make sure I order the right switch, I would like to get it's part number.

Thank you for any helpful advice.

[500hpgtx]

Hi WilmoedJ!

I will never use a FRAM filter on my car agin. i grew up with FRAM filters as they were heavily advertised. I had a problem with low oil pressure on our 95 3.8L transport. The oil filter restricted the oil and the pressure dropped. I use either a Mobil1 or a Royal Purple oil filter. For the few dollars more, they are definitely a superior filter. I would start there first...cheers KEV

[WelmoedJ]

I surely will use another brand of oil filter.
However IMO this would not change the current behavior of the humming fuel pump as this seems to be related to the oil/fuel pressure switch.

Any reflections on that specific issue?

[500hpgtx]

JRS3800 stated that he believes the oil senders can become flaky on our vans. He said that he has seen the oil pressure gauge fluctuate a lot even with replaced senders.He said it is not easy to get an accurate sender. He has not seen many failed oil pumps either. His experience is that the pump should last the life of the engine.

I found out that our fuel pump was going bad some time ago when I bought a fuel pressure gauge and measured 20 lbs at the rail. I remember very vividly dropping the tank with 5 gallons or more in it and replacing the pump. Obviously, I would consider checking the fuel pressure as well as the voltage going to the pump. I do not have schematics for the 3.8L TS, but voltage before and after the sender should be checked. I would think that a drop of 2 volts would likely affect the pump. It is more than likely that the pump is failing if it is original.....good luck..KEV

[500hpgtx]

Hey WilmoedJ!,

I believe there is a fuel pump relay as well on the 3.8L TS. You may be able to swap relays with another in the bank at the front of the vehicle on the passenger side, if the relay is failing....KEV

[WelmoedJ]

If the pump starts failing, it would IMO also have a noticeable influence on the car's starting and driving.
This is not the case. It starts and runs without hesitation.
Although this is not proof of the proper pressure, it shows the pressure is well enough to keep the car going.

The only times I heard the fuel pump buzzing/humming before was when the tank was almost dry.
I have noticed a couple of times (after filling the tank) that the fuel gauge needle was jumpy, which could mean spikes in the supplied voltage). The needle jumped to far over the 'full' signal, dropped to about 3/4, returned to normal full and repeated this behavior a couple of times.

There's no signal of the MIL so, if this is something that is part of the monitored system, it seems to be within acceptable limits.

I will check on the voltages at the supply and pump side of the switch.
I do have a fuel pressure kit, but that's for another type of car (early 80s oldtimer) and I may not have the proper connectors to do the test on the TS.

I'll report back once the tests have been performed.
Thanks for the suggestions.

[Tech II]

Remove the oil pressure sender and attach a mechanical gage.....this will tell you if the switch is at fault.....

A fuel gage with wild swings is usually the fuel sender in the tank.....

Humming fuel pump? As they get old, they hum.....have seen regular customers come in with humming pumps, and the pumps lasted a long time after that.....it's basically a crap shoot when the pump actually dies.....key to keeping a fuel pump healthy is never let the fuel level drop below 1/4 of a tank.....

[WelmoedJ]

Originally Posted by Tech II

Remove the oil pressure sender and attach a mechanical gage.....this will tell you if the switch is at fault.....

My first item to do. This sender (I guess you mean 'switch') is close to the oil filter at the back of the engine, isn't it?

A fuel gage with wild swings is usually the fuel sender in the tank.....

Which IMO could be influenced by swinging voltages from the oil/fuel pressure switch?

Humming fuel pump? As they get old, they hum.....have seen regular customers come in with humming pumps, and the pumps lasted a long time after that.....it's basically a crap shoot when the pump actually dies.....key to keeping a fuel pump healthy is never let the fuel level drop below 1/4 of a tank.....

I usually fill up sometime between 1/4 and warning light; no issues in the passed 256000 kilometers, but yes, it can happen the pump gives way quicker because of getting a bit hotter when almost empty.

[LMP]

The fuel pump runs on 2 circuits: ignition relay and oil pressure sender/switch..yes it is a switch for the fuelk pump, not proportional to pressure sender.. The fuel pump will run...or not, never in between. It runs ? then it runs, period. It hums ? if you have pressure and the car runs, that is OK. You can spend the trouble of measuring fuel pressure...about 43 psi....

My oil pressure dial is quite erratic ..has been so for about 3 years now. I blame it on the sender...but will not change it just for that reason. My 19YO car has only 170000 km...110,000 miles...so I have no suspicion at all for the oil pump.

Finally...you've read all about it, FRAM is a no-no, period. My own experience is also in that direction. FRAM = low pressure after 2 weeks. DELCO filter: OK.

mmm.. I did not read all replies in detail...so I might duplicate other's replies.

[Tech II]

Re: TS3.8L 96 oil pressure/fuel pump switch
Quote:
Originally Posted by Tech II
Remove the oil pressure sender and attach a mechanical gage.....this will tell you if the switch is at fault.....
My first item to do. This sender (I guess you mean 'switch') is close to the oil filter at the back of the engine, isn't it?

Yes it is....they call it a sender when it operates a gage.....they call it a switch when there is no gage, just an idiot light....

Quote:
A fuel gage with wild swings is usually the fuel sender in the tank.....
Which IMO could be influenced by swinging voltages from the oil/fuel pressure switch?

No.....the oil pressure switch, is just a backup to the fuel pump relay....let's say, the relay fails,,,,,now the car won't start right away....so as the car continues to crank, oil pressure builds up in the engine and then the switch closes, then sending power to the fuel pump,,,,,,this is a classic symptom of a failed f/p relay, an extended crank....the fuel level gage is a completely seperate circuit......the level sender in the tank is the usual problem.....however, I just remembered from another post, the pass through body connection can sometimes get corroded and cause the same problem.....

[LMP]

Just to be more clear than clear: the oil presure device on the 3.8 carries both a proportional pressure sender (for the gauge) and an on/off switch for the fuel pump backup circuit.
with 4 wires
(The 3.1 oil pressure device has 2 switches..one that gives a meaningless "reading" to the gauge, and the fuel pump backup).
with 3 wires


www.avigex.ca/xport/instrumentpanel1.jpg
www.avigex.ca/xport/fuelinjection.jpg

NOtice also that you can test the fuel pump only with engine OFF by feeding 12V to that red wire (fuel pump prime connector on the diagram) that goes nowhere usually between the EGR valve and the MAF sensor...


BUt...but...I'm just noticing something weird in your original title: '96 TS did not have the 3.8...nor the 3.1: it was built with the 3.4 only........ahhh..yeah....but in Netherland....model year might be different....possibly a '95 labelled as a 96..for the time to go across the pond.... and some european models always kept the sharp front end...93 style..

...but with the Silhouette trim...lacking the traditional Pontiac twin grille...at least in France, this one a '95 with a 2.4 4cyl using propane

while other countries, like Sweden and Netherland, had this style, this one from Tom van Hooft in Vlijmen
,NL


.am I right..which is yours ? .post a picture if you can...

[WelmoedJ]

Sometimes you get more than you asked for.
In this case my car and myself (of course at the driver's side).
Picture taken in the "far east" of my country.
The house is one of the old (and smallest) farm houses in the province of Drenthe.
I also included a picture of my oldtimer.

Did not yet have had a chance to do some work on the car as my oldtimer needed some work done before the next event.

Indeed the car is a 1995 (nov 95 according to the date stamp on the wheels) model, which I purchased August 1996. Mileage is now 159k.
This TS is also on its way to oldtimership.
There not much maintenance waiting expect for the oil pressure issue, which hopefully will be solved after the oil change and new - non FRAM - filter.

I have been looking for the Mobil1 filter for the TS, but the distributor over here only carries their oil, not their filters.
Since the Mobil1 and Delco filters come from the same factory, they could be of the same quality, presumably.
According to the Mobil1 table I could also use one of their filters for my oldtimer. I now use VAG PH7328, which seems to be manufactured by FRAM too.
The oldtimer does not have problems with oil pressure or filter, but on the next oil change I will pre-emptively replace the FRAM with another brand. Officially the manufacturer advised Purflux, but that filter is not available here and besides that, the VAG filter is taller which helps cool the oil a bit more than the shorter Purflux would.

The Mobil1 distributor tells me he is going to see into the filter matter and inform me of the availability in NL.

I already have looked at the oil/fuel pressure switches available on ebay.
Prices there are approx. 10% of what I have to pay to the Dutch GM parts distributor.
Having not yet looked at the switch on my car, I can't tell which type I need (the long 4-pin or the shorter 3-in). I however presume it's the long 4-pin model. Buying on ebay, even with trasnport charges will be cheaper than buying over here.

Once I have info or test results, I'll report them.

[LMP]

Originally Posted by WelmoedJ

Indeed the car is a 1995 (nov 95 according to the date stamp on the wheels) model....

Yeah..in Oldsmobile Silhouette trim....By all usual practice, a car built in nov 95 would indeed be labelled as a '96 but is was obviously built with USA '95 mechanical specs......I guess the wheels are original, hence the date, ...the actual manufacture date is normally stamped on the passenger door end....may '93 for mine....

[LMP]

Originally Posted by WelmoedJ

...My DeLorean is one of the few (approx. 100-150 cars) that have been painted. Not factory though, as the factory didn't have a paint street nor a permit to set one up. Painting was permitted by the big boss, but dealers had to take care of the job.

My Pontiac is a late 95 model and therefore designated as being a 96er.
Most of the problems were in the first 3 (warranty) years, fortunately.
If I'm correct these cars were built in Austria. A week ago I have replaced the spark plugs; man oh man, that's a hell of a job on a 6 cylinder car. Took me about 3 hours for the rear ones.

One of the major changes I made was rewiring the main lights. The factory wiring was way too light to provide good power to the lamps. I rewired using 2.5 mm2 wire and for each unit its own relay. That improved the light by 50%. I also made all units work when the high beam is turned on.

I started doing my own maintenance after I found that the workshop that did service the car previously, never replaced the oil filter (it still had the factory sticker on it after removing). I knew why: the filter seized so tightly that it ruptured totally upon attempts to remove it.

Now I actually don't need a big car like this one, but it drives well, is comfortable and most of all it's worth nothing for trading in. So I keep it as long as possible, at least until the engine gives in. An overhaul is a bit too much for the car's age and for me.

Back to this thread on that topic...The idea athat these were built in Austria is interesting...GM surely has a plant somewhere there.
As for the headlights, I was to comment that at least your DeLorean has standard sealed beams headlights, the type that delivered the light beam where it belongs...and replacement was cheap, with new reflector, lens and bulb....I do not find the profiled light contraptions of todays cars very interesting..blasting the light all across the earth......so inefficient that you need 100W bulbs to try to deliver what was obtained with a 30watt sealedbeam... ANd indeed, right from the start, I had installed relays for my TS headbeams, fed directly at the alternator output, with all units working on HI ; all the internal wiring just feeds the relay coil; what a difference..I had done the same for all my cars for decades. ..but those modern plastic lenses are doomed after the years anyway. I've seen cars of similar years in Europe that still had glass lenses....how about yours ? (90 to 92 had glass lenses here...93 and on... plastic.

[WelmoedJ]

Originally Posted by LMP

Back to this thread on that topic...The idea athat these were built in Austria is interesting...GM surely has a plant somewhere there.

They also had plants in The Netherlands (50s/60s), Belgium (Opel) and other countries. But that was then and this is now...

As for the headlights, I was to comment that at least your DeLorean has standard sealed beams headlights, the type that delivered the light beam where it belongs...and replacement was cheap, with new reflector, lens and bulb....

European laws do not allow for sealed beam units for the low beam, so imported cars (from the Americas) have to exchange their light units for H4/H1 or whatever is applicable to European models of the car's brand.
Mind that the DeLorean only had a roadworthy approval for the US, not for Europe (the application for EU roadworthiness died with the factory's bankrupty).

I do not find the profiled light contraptions of todays cars very interesting..blasting the light all across the earth......so inefficient that you need 100W bulbs to try to deliver what was obtained with a 30watt sealedbeam... ANd indeed, right from the start, I had installed relays for my TS headbeams, fed directly at the alternator output, with all units working on HI ; all the internal wiring just feeds the relay coil; what a difference..I had done the same for all my cars for decades. ..but those modern plastic lenses are doomed after the years anyway. I've seen cars of similar years in Europe that still had glass lenses....how about yours ? (90 to 92 had glass lenses here...93 and on... plastic.

My Pontiac fortunately came with glass lenses. They're still on the car from new. While replacing the lamp units wiring I also found crappy plug-to-wire connections: not solid metal-to-metal but some half burnt insulation. This had affected the reflectors a bit thus decreasing the light even more. Well, that's over now.
The new circuit is powered from the main 12V connection at the driver's side inside wheel well, as said has a relay and a fuse for each of the units.
All of the light units have H4 (by law for this car in Europe).
I do not see need for Xenon head lights, though they may have better light. Using Xenon would imply replacing all of the units for Xenon approved units, way too expensive for a car of this age (16 yrs).