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Discussion Starter #1
Hello,

I know oil pressure gauge readings being low is a known problem and has been covered on the forum. Usually people discover it's an oil pressure sender, not my case, a little background, the previous owner or dealership at some point went through extraordinary lengths to conceal the oil gauge problem. I discovered the gauge cluster had the bulb removed and even the center with the speed o and tach taken apart to get to the oil light bulb. Even the needle on the oil gauge was forced to the right to show a higher reading. Butchered cluster, it was missing stoppers on the oil and volt gauges. Some of the faces gouged, the gear indicator had lcd segments missing, the speed o was sticking, and the tach was off by 1000 RRM, and it too sticking throughout the range.

Fortunately I was able to get another gauge cluster from a wreaked GS spyder and after installing, it unveiled my suspicion, the oil pressure reading is a blaring problem.

Here's what I've done and the problem still exists, I replaced the oil sender with a comparable VDO sender. The VDO oil pressure sender works like the stock one.

I've noticed at times the gauge works fine, when warmed up it'll drop and stay at the 1/4 mark at idle. Then sometimes it'll drop to zero and both oil lights comes on. I discovered the other day when it's holding at 1/4 at idle, it'll drop to zero when I turn the headlights on. If I turn them off it goes back to 1/4.

Seems intermittent and likely a grounding problem, I just don't know where I should be looking to find the ground straps around the engine. Any other experiences how to resolve is welcomed.
 

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I'd be looking for a connection issue at the cluster. Your starter would reveal an engine ground problem long before the oil pressure gauge would due to the extreme amperage difference between the two. The connections on the gauge cluster is not ideal due to the way they used that flexible plastic pcb material and the traces themselves are one half of the connector. Your headlights may be affecting the gauge simply due to the light coming on in the cluster. The increase load of the indicator could be enough to arc the gap and make a better ground connection when it's on. I'd bet your problem is there or on the main harness firewall connection. It's worth hitting both with some electrical contact cleaner IMO.
 

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I agree with tcrote this looks like an electrical issue.

*Assuming* you have correctly checked the oil level, you can rule out 'both the lights' coming on as accurate.

If you want to rule it out totally, you can get a mechanical reading done and demonstrate that the pressure does not drop on the mechanical gauge when the drops happens on the cluster, but given that it's (I assume) consistently observed I really can't see you actually have an oil pressure issue.

Disclaimer: This advice is worth exactly what you're paying for it. I reserve the right to be completely wrong ;)

C
 

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Discussion Starter #4
I agree with tcrote this looks like an electrical issue.

*Assuming* you have correctly checked the oil level, you can rule out 'both the lights' coming on as accurate.

If you want to rule it out totally, you can get a mechanical reading done and demonstrate that the pressure does not drop on the mechanical gauge when the drops happens on the cluster, but given that it's (I assume) consistently observed I really can't see you actually have an oil pressure issue.

Disclaimer: This advice is worth exactly what you're paying for it. I reserve the right to be completely wrong ;)

C

Yes, oil level is fine, I changed it few weeks ago shortly after I put the replacement cluster in. I had cleaned the connections on the cluster when I installed it. But I'm going back and check the ground, I may run an added ground wire off the gauge and see what that does.
 

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Discussion Starter #5 (Edited)
UPDATE:

Ok, I ran a couple extra ground lines off the cluster, no change. So I busted out the multimeter and starting checking voltages at various points on the cluster and at the battery. My suspicion is confirmed, the car has a weak charging issue, noticeable at idle. I'm leaning towards the alternator being the issue.

With the car running I checked voltage points on the cluster at various gauges, when it's at 13.5 volts with hot oil and at idle, the oil pressure gauge sits at about the 1/4 mark and it's fine. But, when turning on accessories or the engine fan cycles, the voltage drops. When the engine fan kicks on it drops to 13.3 volts, add the headlights on it drops further, add the A/C blower even further. At the battery with all the accessories on, I'm getting 13.1 volts. Of course, during this the oil pressure gauge drops to zero and I get both lights.

The oil pressure gauge is calibrated to work with 13.5 volts, any less or more it throws off the reading. This is the conclusion I've reached, any other knowledge or input I'm open to.

In the meantime I'm on the search to acquire an alternator, any recommendations is welcomed. It looks pretty straight forward to remove/replace, so I'll be doing that myself.
 

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13.1 doesn't sound like a huge drop to me, but perhaps someone else can confirm. Certainly I'd not be going for an alternator replacement based on that.

Earlier you said that the gauge drops when you have the lights on only? Was this the case, or do you need to turn everything on?

C
 
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+1....That doesn't sound like the issue...Have you checked the voltage drop between your engine and the chassis or inspected the ground strap between them? You need to check the voltage drop under load...Not the resistance, but the drop....Google it if your unsure how do it....Jason
 

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Discussion Starter #8
13.1 doesn't sound like a huge drop to me, but perhaps someone else can confirm. Certainly I'd not be going for an alternator replacement based on that.

Earlier you said that the gauge drops when you have the lights on only? Was this the case, or do you need to turn everything on?

C
The voltage drops when anything is on, lights, radiator fan, A/C blower. With everything off it holds 13.5 volts and the gauge is fine. Any accessory on it drops about .2 to 13.3, add more +1, +2, etc will drop it nearly .5 getting close to 13.0.
 
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That is not what I'm talking about...The voltage is dropping across the battery because of increased load, that is normal....You need to see the voltage drop across the ground circuit..Go on you tube and look for videos on how to check chassis grounds...Jason
 

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Discussion Starter #10
+1....That doesn't sound like the issue...Have you checked the voltage drop between your engine and the chassis or inspected the ground strap between them? You need to check the voltage drop under load...Not the resistance, but the drop....Google it if your unsure how do it....Jason
Where to look for ground straps running engine to chassis on this vehicle? anybody have a diagram that shows the ground points? There should be a several I'm sure. I've checked voltages everywhere but on the engine. What's a good point on it to check? coming off the alternator? positive line to the starter? The voltage readings at the dash/cluster and the battery have matched, but I haven't checked it on the engine.

My initial suspicion is a grounding issue, I've ruled out the sender and the gauge, that's not the issue. I'd think if I truly have a vehicle grounding issue, I'd have some drivability issues, stalling out, not starting, etc, which is typical when there's a bad grounding with engine to chassis.

The reason I was starting to lean towards an alternator problem is the voltage drop under load. While cruising the other day I turned on the a/c blower to high and the lights while watching the oil pressure gauge and the voltage drop slightly. Same way it'll do while sitting at idle.

I thought it was possible to have a low amperage output alternator, but my experience has always been they fail suddenly and you know it when it happens.
 

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Discussion Starter #11
That is not what I'm talking about...The voltage is dropping across the battery because of increased load, that is normal....You need to see the voltage drop across the ground circuit..Go on you tube and look for videos on how to check chassis grounds...Jason
Got it, I'll do that and check the voltage drop across the ground. I'm going to chase it until I find it, I think I found the reason why this car went to auction a few years ago. Irritating the lengths someone went through to hide it. I only noticed it when the oil light bulb(s) had been removed and when looking closely the gauge cluster being hacked up. Unfortunately I didn't see it when I bought it, otherwise I would have passed.
 

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Hi,
Same issue with my GS from 2007 and your feedback and updates will be very appreciated.
Cheers Fabrice


Envoyé de mon iPad en utilisant Tapatalk
 

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Discussion Starter #16
Well today I spent some time tracking this issue down. Still no change but here's what I've done thus far, I located two 13mm bolt grounds in the engine bay, one on each side that's located in the top area near the hood props. I took the bolts outs and cleaned them, didn't look bad. I did the same with the one mounted close to the battery. I also bypassed the factory disconnect which is between the battery neg and chassis ground, still no change. It takes all of a few minutes to accomplish, but I put it back inline afterward.

I couldn't find it today, but I know there has to be a ground line going from the engine or bell housing to chassis. I'll look again tomorrow when i do a wash on it, if anybody knows where it's located, please chime in. I'm not finding it.
 

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Discussion Starter #17 (Edited)
UPDATE:

I finally resolved this issue!! I never found a ground strap from the engine to the chassis. My DMM was showing a non existent ground to the engine. I grabbed a 10 gauge wire and ran it from a bolt on the alternator to the ground point on the right side of the engine bay, near the hood prop. Started the car, let it idle and turned everything on, blower on high, seat warmer, headlights and waited. Immediately I noticed the difference, once hot oil and the engine fan on the lowest the oil pressure gauge would drop to is just under 1/4 reading, and no oil warning lights!!! now at idle, with a load the alternator is keeping the voltage between 13.5 - 13.8 at the battery.

I'm going to purchase a couple 24" braided ground straps and replace the temporary wire I ran. This vehicle had this issue for a long time, likely why it went to auction a couples times before I bought it from the dealer in PA. On the face looks like an oil pressure issue, but it's not. The only thing I can think of is it manifested after the clutch change or something. I seriously can't find that ground line, I'm getting back under it one more time this weekend and look for it.

Thanks for all the input, glad I didn't replace the alternator, that wouldn't have fixed the issue, cost me about $70 because I first replaced the oil sender thinking that was the issue.
 

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Great post, I wonder how many Maserati owners are thousands poorer due to similar issues and the dealership pocketing the vast $$ for looking. I also wonder what diagnosis there might have been. Thanks for your post and thanks forum.
 
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