Hi there, I am new to the forum but have been helped many times by reading previous posts so now that I really can't find an answer for this I thought I would come here.

I have an intermittent crank/no start condition that I have a feeling is fuel pump related. Every time it happens my thought process is the same: Check for trouble codes then test fuel pressure. But every time it happens I test for trouble codes, there are none, and then it starts fine, so I can't do the fuel pressure test. During the test procedure the fuel pump whirs just like it is turning on, then a few seconds later whirs again. So does anyone know what it is doing? Or better yet, have a source for finding out what the self-test actually consists of?

I know that next time it happens I can just do the pressure test first but I'm trying to get a leg up on this thing because my current job may require me to travel on short notice.

Thanks,
Kiernan

 

This is an excellent Link for trouble-shooting problems with this era engine. *Bookmark it.

Been through a similar problem that your experiencing now. Came down to a problem with the MAP sensor. The MAP takes it's reading from intake vacuum, creates an electrical pulse that the ECU reads, if there is a problem with the reading of the vacuum, the ECU will shut down the fuel pump.

In short terms, if there is no vacuum, the fuel pump will be shut down so the engine will not run. Kind of acts as a 'CrankShaft Position Sensor'

You will not get any codes from this thru OBD I scanner.

The fuel pump will pressure up at turn of the key, for start up, if the MAP is not sending the correct signal, at cranking, the fuel pump relay will be "turned off" and the fuel line pressure will drop out with cranking.

Check out that link, read up on the testing of the MAP (page 2) OR just replace the MAP, it's a $30 aftermarket part.

But, first, check the vacuum line that comes off the intake vacuum tree, if the line is cracked, dry-rotted, Replace the line, Check all small vacuum lines, or even replace them, 6 feet of 3/16" vacuum line will do the entire 5.8 engine.

 

Hey, thanks for the reply, I actually tested the line to the MAP sensor, and it holds vacuum well, and the MAP sensor seems to output a frequency that corresponds with the value I have in my repair manual (it seemed like the freq was always about half of the given value, but they were using an automotive tachometer and I was using an oscilloscope so I assumed it was a number of cylinders issue).

Just to be clear, what I meant was that performing the self test that happens before the code readout seems to actually fix the no start issue. That is why I was asking if anyone knew of a source to find out what exactly happens during that test, especially the fuel pump.

Also, the problem seems to not cause stalls. (It did stall once in the last few weeks whereas the no start issue has happened maybe 8 times so I am troubleshooting it as a non-stall related problem for the moment). This leads me to believe that it is either an electrical issue that happens at battery voltage but not alternator voltage (such as a failing fuel pump motor) or a fuel delivery issue that occurs after fuel has been stationary in the lines (some type of blockage or I was wondering if there is a check valve that protects against excess pressure which may be stuck open - again need to check pressure when problem occurs).

Thanks for the reply, and sorry that mine may be delayed due to remote work locations and internet access issues!

Kiernan