Da Mail Man

Greetings All...been a while,

1)...1988 vette coup, 350 auto.....currently 101k orig miles.

2)...bought the car with 86k orig miles and all receipts and paperwork a few years back.

3)...Running mobile 1 synthetic 10-40 with regular oil changes not exceeding 4k miles.

5)...Have removed distributor a few times to check on possible wiring issues and issues involving cold start/no start and just long crank time starting.

6)...I have rebuilt dash cluster almost a year ago.

PROBLEM/ISSUE:

I have noticed that my oil pressure reading (which level is full) seems to fluctuate quite a bit.....I have no valve clattering or tail pipe smoking and minimal pan seal leak(s).....I actually had the red warning dash indicator light come on momentarily and noticed that the oil pressure READING on the dash was at 9psi (when I looked at it) while I completed stop at light with ac on in 92* temps.

Now, I know that the car will not start when oil pressure is below a certain psi and I believe that this may be tied into the oil pressure sender in the block nearest the back of engine and distributor. I also know that the fuel pump is tied into the oil pressure if I remember correctly.

JUST A PROBABLE RELATED HISTORY:

I have had START (long crank cold or hot and no start) issues many a time thinking it was the ignition module in the distributor and strangely, after removing the dist cap and simply removing the module and reinstalling it, the car would start right up! I ran a separate ground wire for the distributor just to play it safe.All the guts of the dist have been replaced and tested. I have even grabbed the "bulk wiring" behind the distributor and shoved it around a bit and car would start right up. (I am NOT looking for responses to hard starting).

So, with that in mind, would anyone think that the oil pressure issue as mentioned above, could be as a result of a bad oil pressure sender or a loose connector to it? Oil pump or pump screen issue?

Thanks for any replies and to note, **If I type in caps to a response, it only serves to segregate sections of the conversation and is NOT yelling.

Tom400CFI

That is not true. Car will absolutely start with 0 oil pressure.


Yes, there is an oil pressure switch, that when ~4PSI is reached, closes, and sends power to the fuel pump. However, that is as a "back up" to the primary fuel pump power circuit, which has a relay, controlled by the ECM and sends power to the pump.


It certainly could be. The way to test that would be to hook up a mechanical pressure gauge to the oiling system and see what your actual oil pressure is. If it aligns w/your digital read out, then you have a mechanical/hydraulic issue. If it doesn't, then you have a sending unit/electrical issue.

Da Mail Man

i figured it would/could be but, wanted to bounce it off the forum. I may change out the sender as it does have some age and mileage on it and is located where the wiring harness i mentioned i shoved around is.

Tom400CFI

The sending unit sends information to the dash. It is the unit near your distributor. The oil pressure switch is for back up power to the fuel pump. That could be located just above the oil filter, or by the sending unit, or as part of the sending unit.

WVZR-1

The larger "bell shaped" sender with the single spade connector is for the gauge on an '88.

Da Mail Man

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VERY COOL!...I was just looking at a replacement for same....Hope it is not in too tight...Maybe i can grip it and muscle it out and, i think i have to remove the dist to do so.

Da Mail Man

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Very good as I was wondering which specifically did what.

Rockcrushervette

My 88 was reacting the same also as driving down road @70mph pressure would be 45 then drop down to 32! At a light it would be 12 or so then just drop down to 3,4,9! I change the sending unit for the dash single wire! Everything is running normal!

Da Mail Man

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DAMN! (just like mine!)...I hope (and suspect) that could be the case and cause in my situation!..Thanks for the response and all the forum responses...Will purchase and see if I can install over w/e....Any difficulties in removing/installing?

WW7

Advance Auto sells a socket to remove the sender on your car..Makes it much easier to get out then using a wrench...WW

vader86

On mine I saw such strange behavior first from a sending unit failure, checked with a manual gauge to see if it was actually making good pressure and it was, but then later found the connector itself needed to be cut out and respliced back in.

Da Mail Man

Greetings all,

Well, i did the oil sender for dash replacement today and all is well. A few snags as I found myself having to dismantle the wiper screens just below the hood, had to remove wiper motor, and had to remove the distributor. Unit came out fine after applying PB Blaster to it and letting it soak while i was setting up for all this. Figured it would take an hour at best---WRONG!

Here is the embarrassing part.....I have my wires marked properly, I have a light colored distributor cap that I took a magic marker and marked which wire goes to what tower, noted the position of the dist housing and the position of the rotor and pulled the distributor (for access to sender unit).

Now, the engine was not disturbed but, for some unknown reason (this statement doesn't seem logical, based on what is to follow!), when I dropped the distributor back in the engine, the housing was in the same position but, the f'ing rotor was not (yes, I know it has a rotational twist to it)! It did fire however but, ran crappy.

Dist gear is tight and I know I didn't jump time. The only thing I could think of is that in some bizarre unknown way, I must have looked at all this "sideways" in my head! Well, after pulling the distributor again and rotating in 180* to see if I put it in "180 out", it would not start - only sputtered, etc.

I put it back the way it was originally and would up shifting each plug wire over 1 tower position, timed car, reconnected est wire and all is well. Glad i don't have to do this every day. Tomorrow, will re-mark distributor and re-assemble everything. Again forum, thanks for the assistance.

65Z01

Before you drop the dist. back in rotate the rotor slightly CCW, as the dist. slides down into position the rotor will rotate CW.
I like to apply 3 marks before pulling the dist:
-one on the dist. base & intake base
-one on the dist. base for rotor position before removal
-one on the dist. base for rotor position after removal

I've recently noticed oil pressure is lower than earlier this year and having hard start issues too. Looks like time to replace both those oil pressure units and maybe remove & clean the stem into which both are screwed.

Da Mail Man

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Thanks for the reply but, this has been resolved.

Before you drop the dist. back in rotate the rotor slightly CCW, as the dist. slides down into position the rotor will rotate CW.
YES, I AM AWARE OF THAT AND I BELIVE I STATED THAT IN AN EARLIER POST/REPLY.

I like to apply 3 marks before pulling the dist:
-one on the dist. base & intake base
-one on the dist. base for rotor position before removal
-one on the dist. base for rotor position after removal
I EYE-BALLED IT BUT - WELL - RE-READ MY POST.

I've recently noticed oil pressure is lower than earlier this year and having hard start issues too.
I HAVE HAD THIS ISSUE SINCE OWNING CAR BUT, SEEMS TO HAVE GOTTEN MUCH BETTER FOR SOME REASON. EVEN EXPERIMENTED WITH COLD START INJECTOR.

Looks like time to replace both those oil pressure units and maybe remove & clean the stem into which both are screwed.

Read more: https://www.corvetteforum.com/forums...#ixzz3qWLpTBEz