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Oil Pressure Problem

B

Banshee

Active Member
OK peeps. Car runs fine with oil pressure but the problem comes when it sits for a while and go to restart. Very hard to start and doesn't kick over until the oil pressure comes up. Takes 3 or 4 times of turning over and as the gage comes up the car starts and everything is fine until several hours later when going to start again.:disgust:

I have to get the manual for this baby but until then, you guys are my support group. I am told that it's the oil pressure sending unit or the oil pressure switch. Well, in an effort to cross compare I looked at a Grand National to see where the oil pressure switch is located.........NOT in the same spot. SO anybody have any ideas? Am I on track with the oil pressure switch and where is it located?:DontGetIt:
 
The oil pressure sender should be on the passanger side next to the front cover. I think if you follow the skinny oil tube down from the turbo you will get to a brass block with the electronic sending unit for the oil pressure gauge. Should be down in that area, next or close to the oil filter, slightly above and behind the filter. This is just going on memory so keep that in mind.

Good luck
 
Yep just looked there. Following the oil tube from the turbo, it does go to a brass t-block behind the oil filter on the engine block,,,,,,,,,,,,It's not there and there is no harness dropping down to that area to make me think it was taken off and just not plugged in. Keep in mind that I am reading oil pressure, just not when I'm trying to start

Took an illustration from Turbobuick.com and it shows what you have described but I guess the TTA setup is different. The Hunt Continues.
 
The oil pressure sensor for the TTA is on the engine oil cooler setup where the oil filter sits ... long round sensor and if the original one it's metal casing if a later replacement its a black plastic casing on it.

The brass t-block you are referring to is where the GN sensor sits; the TTA have just a plug in that hole as I'm sure you noticed ;)
 

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Your barking up the wrong tree I believe....the "C" terminal of the sender is merely used as a back up 12V supply to the fuel pump should the fuel pump relay fail, or the ECM has a faulty fuel pump relay drive.....while already running.

So, an extended crank time would indicate that the oil pressure sender IS working when pressure is sensed and the switch closes the circuit to the fuel pump allowing the car to start.....so it's not the other way around.

You may have a faulty fuel pump relay, but it's an easy diagnosis....key off for 30 secs and key on (dont crank) you should here the fuel pump run for 2 secs then shut off because the ECM sees no crank sensor activity,okay??


But it's my opinion that you have a hot soak "bypass air" issue with the Idle Air Control motor (IAC)....and you can *maybe* diagnose that by next time giving the accelerator pedal an ever so slight push to crack open the throttle plate while cranking it over....but a very light touch on the pedal.

But also...what do you mean by "sits for awhile"? like an hour after running? or weeks after running.....you may have fuel pump issues then.
 
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I have witnessed it. Hard start I would say it is longer than 5 seconds or so. We were at a car show and it was only maybe 4 hours and it had a hard start.

Banshee I have Both Service Manuals, If you need a certain section I can text you the pages... just let me know.
 
No need....I have both service manuals as well.

Buy the oil pressure sender. Good Luck!

Edit: I see you were offering up yours...nevermind....my appologizes.


6E3-A-22
 
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I did get the oil pressure sender. Been working too much and haven't had a chance to change it yet. The car gets hard to start after sitting for a few hours like at cruise nights or even just over night.

I will check the fuel pump relay when I get home from work. WHere is the IAC sensor located. I remember cleaning this sensor on my Expedition and troubles went away.

My Manuals have been ordered but have not shown up yet. I know I have you guys for support but it's getting hard fishing around in the dark. Thanks you guys for the comments. I'll be changing the Oil sensor later today.
 
OK,,,Changed the oil pressure switch under the oil filter. I have no change in the hard to start dept. So by previous suggestion, I turned the key to on without cranking and DID NOT hear the fuel pump come on. So this is the Fuel pump relay??!!!!

Now for the next question, WHere is this relay? and the location of the IAC sensor. I also slightly touched the accelerator pedal while cranking and it made no difference in my start problem, but don't want to do too many things in an effort not to know what causes or corrects the problem.
 
Fuel pump relay is located next to the brake booster on a bracket...furthest foward relay.....this will solve your problem, if not it's the ECM fuel pump driver...which means a new ECM.


Fuel pump not running for 2 seconds confirms your hard start problem.
 
x2 fuel pump relay,with the ignition on engine off you she hear the fuel pump turn on if no faulty fuel pump relay.
 
Okay,,back again! Changed the fuel pump relay as per description and location. It did start a lot quicker but still did not hear the pump when turning the key in the on position. I do hear the pump shut off when I turn the car off after it's running.

I'll check it again tomorrow when I get off work. We'll let it sit overnight and then try to start it. Hope this is it. Just concerned about not hearing the pump in the on position. Keep ya posted. Sorry for sounding juvenile about this. I can take the car apart blind folded but I suck at troubleshooting electricals.
 
you will hear the pump turn on,make shore you have the door open and just lisen for a winning noise ,you will really have to pay attention it's only for about 2 seconds or so.
 
Stock or original pumps are considerably less noisy than an aftermarket pumps like walbro...confirmation may require another person bent down under the rear of the car, listening for the pump running.
 
I've let the car sit for a couple days due to working nights. Went out this morning and tried to start and She is still hard to start. To begin again,,,Love it. I have contacted a local TTA/GN nut not far from my home. Since I have no diagnostic equipment, I'm going to bring her in and see what's happening. I don't want to spend a small fortune changing parts and still not know what's happening.
 
UPDATE---- I never had a chance to bring her into the shop due to working so much but yesterday my shop manual came in. Started in on her with the book and SHAZAM!!!!!!!! IAC sensor was the trouble. The stuff that came out of it while cleaning it was amazing. Now she starts up the first hit on the switch.

Thanks to all that replied to my condition and very happy it wasn't something serious.. Now I get to start on the real fun stuff of go fast crap!!
 
Banshee said:
UPDATE---- I never had a chance to bring her into the shop due to working so much but yesterday my shop manual came in. Started in on her with the book and SHAZAM!!!!!!!! IAC sensor was the trouble. The stuff that came out of it while cleaning it was amazing. Now she starts up the first hit on the switch.

Thanks to all that replied to my condition and very happy it wasn't something serious.. Now I get to start on the real fun stuff of go fast crap!!
Click to expand...

Did you clean the IC as well ? , glad you got it runnnig well.
 
Cleaning the Intercooler is a must especially if it has never been done before! Not that hard to do but worthwhile.
 
I use paint thinner...pour it in, shake it side to side and up and down, hose it out , flip it over and let it dry good. When oil quits coming out your done.
 
Cool I will definatley get this done. The previous owner said that the IC was cleaned but judging by the interior of the up pipe when I cleaned it, I would have to say the IC is coated with residue. Anybody will say anything to sell something. That's ok.....If he didn't care enough about the car,,,,I certainly do. Thanks Guys
 
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