The no-start riddle: Cranks but doesn't start, leave it for a while, it starts fine.

[leg396]

Dear 91 legend fans and experts,

I have read all the threads about this common problem but I am still puzzled by my baby's behavior. I narrowed down my problem to be correlated with the fuel pump whenever the car doesn't start. But what drives me nuts is that sometimes it starts and sometimes it doesn't. This happened when it is cold (45-55 F). It happened at the start of the day, the middle of the day and at the end of the day. What drives me even crazier is that when I jump it, it starts. I just bought a brand new battery from the dealer as I initially thought it to be the problem. I have desoldered and soldered my main relay. It is starting fine now but I am afraid of it not starting on me again. Moreover, whenever she refuses to start, I still hear one click by the main relay (even before the soldering) but cannot hear the fuel pump.

My questions are:
1- why does the car start when jumped if the problem is fuel-pump related?
2- Can the malfunctioning of the fuel pump be a sign it is going bad?
3- I am wondering if my soldering was even necessary as the main relay used to click when the car didn't start, was it? Does clicking mean that the relay is fine? Or can it be clicking while not delivering the required voltage to the pump?
4- If she does it again and doesn't start, what should my next step be? (new fuel pump expensive)

Thanks kindly for all the help in advance and may this forum thrive and be blessed forever.

[Daniel_S]

1- why does the car start when jumped if the problem is fuel-pump related?
->The voltage is higher when jumped due to the running engine of the other car. If you put the jumping ground cable not to battery ground but to engine ground, you might have a corroded ground cable between battery and engine.

2- Can the malfunctioning of the fuel pump be a sign it is going bad?
->Theoretically yes, but in most cases it works or it does not. You might want to measure the voltage directly at the connector to the pump using a voltmeter or a lamp. You might also want to measure the fuel pressure using a gaudge connected to the port of the fuel filter (very comfortable in the Legend compared to other cars). Voltage but no pressure->pump is broken. Since pressure is stores for quite a loing time, you could crank the engine and if it does not start, open the hood and read the gaudge.

3- I am wondering if my soldering was even necessary as the main relay used to click when the car didn't start, was it? Does clicking mean that the relay is fine? Or can it be clicking while not delivering the required voltage to the pump?
->The broken solder joint is located at the high current contact, not at the coil. For this reason, even a broken relay will click.
4- If she does it again and doesn't start, what should my next step be? (new fuel pump expensive)
->Measure fuel pressure and voltage at fuel pump. Measure injection pulses at at least one injector. Remove a coil and check for high voltage spark.

[leg396]

Originally Posted by Daniel_S

1- why does the car start when jumped if the problem is fuel-pump related?
->The voltage is higher when jumped due to the running engine of the other car. If you put the jumping ground cable not to battery ground but to engine ground, you might have a corroded ground cable between battery and engine.

2- Can the malfunctioning of the fuel pump be a sign it is going bad?
->Theoretically yes, but in most cases it works or it does not. You might want to measure the voltage directly at the connector to the pump using a voltmeter or a lamp. You might also want to measure the fuel pressure using a gaudge connected to the port of the fuel filter (very comfortable in the Legend compared to other cars). Voltage but no pressure->pump is broken. Since pressure is stores for quite a loing time, you could crank the engine and if it does not start, open the hood and read the gaudge.

3- I am wondering if my soldering was even necessary as the main relay used to click when the car didn't start, was it? Does clicking mean that the relay is fine? Or can it be clicking while not delivering the required voltage to the pump?
->The broken solder joint is located at the high current contact, not at the coil. For this reason, even a broken relay will click.
4- If she does it again and doesn't start, what should my next step be? (new fuel pump expensive)
->Measure fuel pressure and voltage at fuel pump. Measure injection pulses at at least one injector. Remove a coil and check for high voltage spark.

Yet another reason I LOVE this forum. Thank you so much for the professional and rich reply. I really appreciate the time you put into it.

Just a couple of more questions:

1- Where is the pump connector where you advise to measure the voltage?
2- If the high voltage from the running car succeeded in jump starting my car, then wouldn't you think it's less likely to be the pump?

I am just really hoping it was my relay.

Thanks a lot.

[BIGBOY]

The two most common reason are bad main relay or ignition switch.

If you didn't resoldering the main relay correctly it will still act up, sometimes they can't be repaired.

If you can take a picture of the board showing the solder joints.

If it's the ignition switch hold the key in the "start" position, if it runs then shuts off after you let the key go that's the problem.

Also if the ignition switch is bad when you turn the key to the "II" position the dash lights won't come on. (cel, srs, etc.)

[Daniel_S]

The connector to the fuel pump is located under the maintenance cover. The rear seat has to be removed to gain access. I do not think the pump is faulty until you have 12V and there's no fuel pressure.

If the problem occurs again, measure 12V at the connector to the fuel pump. If this voltage is missing, you might want to measure the voltages directly on the main relay PCB:
-PIN 5: With the ignition turned on, you should measure 12V here
-PIN 1: 12V from battery
-PIN 3: 12V from relay to ECU
-PIN 7 supplies 12V to fuel pump.

[leg396]

Dear all,

Thank you so much for the rich and helpful information. I truly appreciate it. I re-soldered the main relay's PCB after seeing cracks around many joints. I believe I did the job right as it has been starting now just like before with no problems. It has been more than a week now, so I hope it doesn't happen again. When the problem was there it would refuse to start almost every 2-3 days, and sometimes, more than once a day. So, I hope my problem is now resolved. However, I still think I have a ground problem cuz the rpm idles at about 700 and I am tired of hearing this humming noise. I am just not sure if it's the engine's normal sound or one of my grounds is poor.

Thanks again,