Occasional problem of the device freezing and not responding.

[five5nuclear]

Today, my brother contacted me with a problem with his 1997 Mercury Grand Marquis equipped with a 4.6-liter engine. He informed me that the automobile sometimes has a delay in starting after being left overnight. According to him, he perceives the sound of the fuel pump activating and deactivating each time the key is turned to the "run" position. He attached a gauge to the fuel rail and measured a pressure of 37 pounds when the key was switched on, after which the fuel pump stopped. The pump must be equipped with an integrated pressure switch, since I was unable to locate one on Rock Auto. When the engine is running, he failed to inform me about the exact pressure, but it must be about 37 pounds since he said that the vehicle performs well at high speeds.

According to him, when he disconnects the vacuum line from the fuel pressure control valve, the pressure increases to around 55 pounds. Additionally, he said that by maintaining the gauge on the rail, the pressure decreases to around 3 pounds from 11 am until around 9 pm. I consider this to be a typical decline.

I attempted to determine if this automobile is equipped with an ignition relay, since its potential failure might be causing the starting issue. If not, what other components should be inspected? The automobile is not present in my garage. Attempting to convey concepts to him over the phone proves to be challenging. He has an assistant who is currently unable to come up with any new ideas.

I repeatedly inquired if he could see the activation of the fuel pump each time he switched the key to the "on" position, to which he affirmed and noted its subsequent automatic deactivation. That is typical. However, it consistently fails to start each time after being left idle overnight. According to him, after the initial run and warming are completed, the engine will consistently start on every subsequent attempt. Furthermore, I instructed him to have his associate inspect the IAC. I inquired if the vehicle would consistently begin its operation when the accelerator is pressed, but it seems that he is rather perplexed about this matter. as it may perhaps be the International Astronautical Congress (IAC).

If anybody here knows of further locations to investigate, I would really appreciate your input. Thank you.

[ponchoT]

One potential cause might be the coolant temperature sensor.

[five5nuclear]

Thank you for your response. However, he said that he did not possess any codes. Wouldn't a coolant temperature sensor trigger a fault code? During my study, I discovered that the IAC may be a potential solution, but I was unable to find any corresponding scripts. Alternatively, the individual assisting him explicitly said that there were no codes involved. I plan to visit the location and connect my scanner to get real-time data and assess the responsiveness of those sensors. Furthermore, it is logical for this phenomenon to occur only under cold conditions. I will inform him promptly, and he may choose to install one for the sake of amusement. Thank you, I hadn't considered that option.

[ponchoT]

The coolant temperature sensor is a component that often does not trigger a diagnostic trouble code.

[five5nuclear]

I encountered these as potential culprits, however it seems that they should trigger a code if they begin to malfunction. I informed him that there could be a potential issue with a coil, where one coil may be malfunctioning while the engine is cold. I do not believe that this issue will trigger a diagnostic trouble code. My S10 did not generate an error code when the coil broke and caused misfires. However, it is possible that one of the cylinders is now malfunctioning and not firing, resulting in a failure to start. The issue seems to resolve itself and the vehicle functions well during the day, but the problem reoccurs after a cold soak overnight. Regarding the crank cam MAF, it seems that they should generate certain codes. Am I mistaken in this assumption?

    To diagnose a crank but no start issue, it is recommended to verify the functionality of the fuel pump and its corresponding relay. Examine the fuel injectors and filters. It is important to inspect the spark plugs and ignition coils as well.
    Malfunctioning engine sensors such as the crankshaft position sensor, camshaft position sensor, and MAF sensor may lead to occasional failure to start the engine.

[five5nuclear]

Alright, because I was unaware of this information, I shall inform him to get an additional item just for precautionary purposes. Installing it is not difficult.