common reason for low fuel/oil pressure?

MarkMoore · Post by **MarkMoore** » February 23rd, 2005, 7:46 pm

i'm in the market to add some gauges to my car via a triple/double gauge pod, and after seeing some fuel and oil pressure gauges, my inquisitive mind got the best of me... what are common reasons for a drop in fuel and oil pressure, and why are both the fuel and oil pressures so important?

also, a pyrometer--y would you want to know the temperature of the exhaust stream?

papa roached · Post by **papa roached** » February 23rd, 2005, 8:03 pm

what would happen if there was no oil pressure, no oil being pushed between the bearings? your motor would seieze, thats why oil pressure is important and as bearings wear the oil pressure drops and without fuel pressure your injectors wouldnt spray right or at all, and low FP can be a bad FPR or fuel pump

Tunes67 · Post by **Tunes67** » February 23rd, 2005, 8:08 pm

A pyrometer would probably be best utilized to keep track of your exaust temps for turbo situations. Making sure that your exaust temps arent to high that your intercooler cant bring the temps down to an acceptable level for proper performance. Just a guess on that one.

Fuel Pressure is critical to proper operation of a fuel injected (and even to carburated) fuel delivery systems. Too much fuel pressure can damage components and/or cause a flooded situation where the carb just cant produce a proper mixture to run. To little fuel pressure and you wont get enough fuel in your mixture.. this is called a lean condition and is extremely hard on exaust valves and other engine components. Being able to monitor your fuel pressure makes it easy to spot potential problems.. example.. if you put high flow injectors into your engine a fuel pressure gauge would allow you to detect if your fuel pump is upto the task of keeping your new injectors fed properly. It would also warn you if your fuel pump was failing. Thing is.. fuel pressure is dicey.. cant have to much or too little.. so you have what is called a fuel pressure regulator. Having a pressure gauge can make it a lot easier to dial in and set your regulator.

Oil Pressure. Low oil pressure is a direct result of engine component failure, whether its due to age, flawed or faulty components or even improper maintenance. If your oil pressure is low its a fair indicator of engine wear due to friction. Oil pressure is important because if your oil pressure drops to 0 your engine will quickly heat up and seize solid without proper lubrication. This can happen from any number of things.. sump pickup blockage.. oil pump failure.. oil leak.. etc..

Tunes67

MarkMoore · Post by **MarkMoore** » February 23rd, 2005, 8:23 pm

hey thanks a lot guys, i really appreciate it... but about the fuel pressure gauge... would it then be pointless to have both an air/fuel mixture gauge and a fuel pressure gauge? because aren't they almost telling me the same thing? i mean, wouldn't it be pretty safe to say that if my fuel pressure gauge was low, that i could bet that the air/fuel mixture was lean, and vice-versa... and conversely, that if my fuel pressure gauge read that the pressure was too high, that i was running rich, and vice-versa?

Tunes67 · Post by **Tunes67** » February 23rd, 2005, 9:04 pm

Umm no.. fuel pressure regulators prevent fuel pressure from being to high. And even if it was too high.. fuel pressure doesnt control how long your injectors spray fuel.. this is controlled by the ECM. A air/fuel mixture gauge will tell you how much fuel is present to a specified amount of air (or it maybe vice versa) this will tell you if you are running lean or rich. Fuel pressure in and of itself will not show your mixture properties. A fuel pressure guage simply measures how "Hard" the fuel pump is pushing the fuel through the fuel lines.

Tunes67

jschrauwen · Post by **jschrauwen** » February 23rd, 2005, 9:19 pm

Tunes67 wrote:A pyrometer would probably be best utilized to keep track of your exaust temps for turbo situations. Making sure that your exaust temps arent to high that your intercooler cant bring the temps down to an acceptable level for proper performance. Just a guess on that one. Tunes67

I'm guessing that a Pyrometer tells the temp of your exhaust gasses. Regardless in turbo application or not, an excessively (hot) high reading would indicate a lean fuel mixture, conversely, an excessively (cold) low reading would mean a rich fuel mixture. I'm not 100% on that.

Tunes67 · Post by **Tunes67** » February 23rd, 2005, 10:02 pm

I'm guessing that a Pyrometer tells the temp of your exhaust gasses. Regardless in turbo application or not, an excessively (hot) high reading would indicate a lean fuel mixture, conversely, an excessively (cold) low reading would mean a rich fuel mixture. I'm not 100% on that.

Agreed.. I just figured it would be more commonly found in turbo applications.

Tunes67

bmwm3guy · Post by **bmwm3guy** » February 26th, 2005, 1:12 pm

Tunes67 wrote:I just figured it would be more commonly found in turbo applications.

Tunes67

You are absolutely correct.

dewthis · Post by **dewthis** » February 26th, 2005, 9:23 pm

With a hotter egt means the fuel is still burning when it enters the exhaust.
This is due to the relation of cam timing and fuel.

matt_fulghum · Post by **matt_fulghum** » March 1st, 2005, 9:54 pm

Another potentially useful gauge is the vacuum gauge for measuring the engine's vacuum in the intake manifold... IM vacuum is essential to the operation of many parts of the engine, and also can give you a rough estimate on things like fuel economy and such.

I'm getting one for my BP'ed MX-3 because I have a feeling that the reason it's dying on me is that I've got a vacuum leak somewhere (I've discussed the problem in my posts on the 4 cyl tech forum)

hgallegos915 · Post by **hgallegos915** » March 1st, 2005, 10:17 pm

get yourself the following gaugses if you are not getting turbo and those extras... voltage guage, oil temp and oil pressure or amp viltage reading? i saw these on cardomain