Mercury Grand Marquis Car Questions Answered by Mechanic-On-Duty – 225 Messages

23 Feb 2015 | Author: | Comments Off on Mercury Grand Marquis Car Questions Answered by Mechanic-On-Duty – 225 Messages
Mercury Grand Marquis

Mercury Grand Marquis

2007 Mercury Grand Marquis Ignition System

New User Asked – My 2000 Grand Marguis stalled on the freeway and would not start back up. It cranks and sounds like it might start but doesn’t. I replaced the air filter and fuel filter. The fuel filter was clogged, but changing these two parts did not change the situation.

I barrowed an OBD II PocketScan Code Reader, but it returned no codes – literally, it said no codes. Before I move onto the next step – replacing the fuel pump – I thought I would ask for other opinions.

Roger – Hello, Please test the fuel pressure and advise the reading. What size engine is in your car please?

You should have 30 – 45psi.


New User – I will have to go out and get a fuel pressure gauge. How long do I have available to respond to your inquiry?

Roger – Take all of the time you need. Thia is not a live chat. I will help you.


New User – I barrowed a fuel pressure guage but can’t figure out where to test the pressure. Two possible ports: One has a tag that says Evap Service Port 1 PSI Maximum Regulated Pressure Only, and the second is part of a line that goes to the radiator. I thought this second one would be part of the transmission fluid system.

Neither port fits the pressure guage, but the fist is much closer than the second.

Roger – Your car has fuel injection. On the steel fuel rail that supplies fuel to the injectors there should be a valve with a removable cap to connect the guage to. The fuel rail mounts on top of the intake manifold.

Does the air inlet tube block your view?

Neither of the two valves you mention are the correct connecting point for the fuel guage.

Any help?


New User – OK, From your description, I think I found the right valve. Now I need an adaptor because it is much smaller than the guage fitting. I need to call my friend to see if he has an adaptor.

Thanks for your help.

Roger – All right. No hurry.


New User – The fuel pressure measures at 39 to 40 on the meter. This would seem it indicate that it is not the fuel pump. Am I correct? What should I check next?

Roger – There is reason to believe with the pressure reading you have the fuel pump is still a good one.

Next would be to check for spark. Have you done this? You said it would try to start but does not. If it tries to start one might assume there is spark. But there are two coil paks right?

Check for spark from each coil. What did you find?


New User – Sorry for the delay, but I had another emergency come up. I did test for spark and was uncertain of the result. The wire to the spark plugs are different from what I am used to from the older cars I have owned and worked on. We inserted a wire into the connection so we could reach metal on the engine.

We got one spark one time of about 4 attampts. The battery has been losing charge a little each day. I’m wondering of this is an important clue. I have hooked up a battery charger.

Roger – Are you disconnecting the wire from the spark plug or from a coil? If you check for spark on a coil connection of a plug wire you need to hold the disconnected wire within 1/4 inch of the coil tower it belongs on. Use an insulated tool to hold the wire while someone else cranks the engine for you.

A bright spark should jump the gap from the coil tower to the plug wire end.


New User – I thought I was testing a spark plug wire, maybe I was mistaken. I will need to wait until tomorroe to check it

Roger – Be careful. Ignition spark is over 50,000 volts. An insulated tool to hold the wire just above the coil tower will guard against getting shocked.


New User – No spark from the spark plug wire. I found in the manual which fuse to check. It was blown and I replaced it. Still no spark. An aquaintance who is mechanically inclined suggested I remove the crankshaft position censor and to check it at a store against one at the store.

Is this an appropriate next steP? Thanks

Roger – Did you check for spark from both coils? Did the fuse you found blown remain good?

Call a parts store and see if they can check a crankshaft sensor to see if it is a good one. If a test is not available then yes, I think replacing the crankshaft sensor would be a reasonable next step.


New User – No, I only check spark from one spark plug from one side. I will check the other side on Sunday. And I will can in the morning also.

Roger – I’ll try to check in for your findings.


New User – The store was not able to test the crankshaft sensor, so I just replaced it. I thought it might have be the problem as the car almost turned over but it did not. What is the next step?

Roger – Its time to test for spark again from both coils. You said prior to replacing the crank sensor you had no spark.

Today you report that it almost turned over. That information raises hopes that there is spark so verifying spark from both coils would be next.


New User – I have spark on both sides, but the car still won’t turn over. Initially it sounds as if it might but doesn’t. There is also a loud pop like a backfire that sounds like it comes from the engine as it tries to turn over.

After that, it may start to get close but not quite the same as the initial try.

If I need to look at another component, please try to describe where to find the part. The manual has given some instruction, but I have trouble finding where it the parts are. No diagrams and the pictures are often different than my engine.

Roger – Let’s try something off the radar. I want to know if this engine can breathe. And I have real concerns now about the length of time the engine has been cranking trying to get it to start. is building up raw fuel in the exhaust at the catalytic converter.

Please remove an oxygen sensor that is in the exhaust header pipe that runs from one of the exhaust manifolds to the catalytic converter. Either side will work. An oxygen sensor is a device that has a short wiring pig tail coming out of the top of it.

The sensor screws into the exhaust header pipe. It remotely resembles a spark plug.

With the sensor removed there is now a place where exhaust can escape without having to go through the catalytic converter. If this opening allows the engine to start (it will be noisey) we can believe there is a restriction in the exhaust that is preventing the engine to breathe.

Will you try this please?


New User – I will give it a try

New User – Is it possible this car has 2 catalytic converters? It appears that there are 2 and the exhaust pipe joins after them before joining with the muffler.

Mercury Grand Marquis

Roger – Yes, there are two. Only one oxygen sensor before one of the converters need be removed for the test I have in mind. If the sensors before each converter are accessable remove one or both as you choose.


New User – Are there 2 sensors on each size? I removed one sensor right before what I thoufht was the catalytic converter. I tried to start the car with no difference. I noticed a second sensor closer to the engine before a turn in the exhaust pipe. I removed that one on the same side as before and tried again.

This time, the engine alomost started up but would not sustain. The back firing was worse too and I could see the air intake from jump when it back fired.

Roger – Try cranking the engine with the throttle closed. If it starts let it idle in hopes it will clear out unburned fuel.

If the spark plugs are badly fuel fouled they should be removed and cleaned. A can of brake cleaner or carb and choke cleaner would work well.


New User – If I understand you correctly, I should not press on the gas when starting the car, correct?

Roger – Correct. A fuel injected car is always best started without pressing the accelerator at all except in very cold weather.


New User – Yea! It turned over and idled for several minutes. It didn’t take hardly any cranking to start up and no back firing. It did idle rough, however.

Could this be becuase both sides are clogged and only one was relieved? I feel we made some good progress. Thank-you.

Roger – The engine will need to run at idle for a while before things begin to clear up. Removing the oxygen sensor from the other side would improve the running of the engine but you may choose to pass on the extra work.

Your car has an exhaust restriction and it may be one or both catalytic converters need replaced. The engine can’t breathe.

I recommend a good reliable muffler shop check your cars exhaust for needs. The car should be towed to the shop.

Anything else?


New User – Not tonight, it’s dark here. I will need to call for tomorrow. Would there be any benefit at this point to allow it to idle longer?

Will that problem clear up if the catalytic converters are replaced?

Roger – Once the exhaust restriction is cleared the engine will start, smoke out the tailpipe, run rough. Let it warm up and then drive it easy as the cylinders burn off the results of the excess fuel. It will clear up but might take 10 – 15 miles before it seems right.

Idling the engine now for a longer period of time will not reward you much. That hole the O2 sensor goes in is just not enough relief for the desired result.


Roger – Hello again,

Please update your question status. Do you need help?

If you are ready to close the question please click on OK to finish up.



Roger – To close the question please click on OK to finish up.

Mercury Grand Marquis
Mercury Grand Marquis
Mercury Grand Marquis
Mercury Grand Marquis
Mercury Grand Marquis
Mercury Grand Marquis

Other articles of the category "Mercury":

Our partners
Follow us
Contact us
Our contacts

Born in the USSR


About this site

For all questions about advertising, please contact listed on the site.

Car Catalog with specifications, pictures, ratings, reviews and discusssions about cars