2000 Ford Mustang 3.8 Intermittent Extended crank/hard start

Alex Technician Colorado Posted   Latest   Edited  
Updated
Driveability
2000 Ford Mustang 3.8L (4) 4-spd (4R70W) — 1FAFP4042YF278980
Extended Crank/Start

Hello guys. I have a 2000 Ford Mustang 3.8 with an intermittent extended crank/hard start condition when the engine is hot. Every now and then it will crank for 3-5 seconds and may or may not run slightly rough just after starting. Originally found fuel pressure dropping off when the key was turned off and replaced the fuel pump. Now fuel pressure holds with key off, but the long crank is still there. Also found spark plugs and cables worn and replaced those. There are no codes setting and fuel trims and data appear normal when the engine is running. I've taken a capture of cam and crank sensors, ignition primary for cyls 1 and 5, and #1 fuel injector. It looks to me like everything is there while cranking so not sure where to go from here. I'm thinking there may be a problem with the fuel but the engine runs well while driving. Any input is greatly appreciated.

0
Glenn Owner/Technician
Texas
Glenn
 

Hi Alex, Codes on a 2000 model Ford seldom help with drivability issues, so it is important to understand the systems dynamics. Even though you have no codes, reset the KAM and perform specified test drive cycles so the systems can perform a relearn. On one of these I would start with cleaning the MAF hotwires with brake cleaner and blow it dry. Verify Intake air temp and coolant temp read…

+1
Ð Awarded
Alex Technician
Colorado
Alex
   

I need to try some of these things when the customer brings the vehicle back. I did reset KAM. The vehicle did behave the same way when I tried disconnecting the MAF sensor.

0
Ð Awarded
Dmitriy Analyst
Ontario
Dmitriy
 

Cam sensor signal is noisy and is somewhat low voltage… Here I filtered it a bit: diag​.​net/file/f3lvxi0wv… ​ Interestingly, the CKP signal is squeaky clean. Not that noisy CMP is necessarily an issue (it could also be just the test leads located near something noisy), but something to think about…

+1
Ð Awarded
Karl Diagnostician
Massachusetts
Karl
   

Image for Techs on their phone to see. Was the coolant system full? Dmitriy, I agree cmp is noisy but the engine was cranking in that image. Also its firing injectors or atleast that one where I think it should fire. I was more curious about the low primary voltage kicks. Thoug this could have been from scope sample rate. Iwould recapture with a much hire samplerate and add coil current

+1
Ð Awarded
Alex Technician
Colorado
Alex
 

Yes, cooling system was full. I'll get all of the ignition primary captures when the customer brings the vehicle back.

0
Ð Awarded
Glenn Owner/Technician
Texas
Glenn
 

Hi Alex, Was the cam sensor ever changed? If so was it indexed with the correct tool? If not, I would home in on the cam sensor and how it is set. There are many You Tube videos performed by actual technicians like Scanner Danner and others that can help you. If the cam sensor is having issues, the engine strategy will allow the engine to run on only the crank sensor signal.

+1
Ð Awarded
Agree
Scott Manager
California
Scott
 

I have seen IAC motors starting to go south do this.

0
Ð Awarded
Jamie Mobile Technician
British Columbia
Jamie
 

What is your spark and fuel pressure doing when you have a long crank? An ignition capture or current ramp of the coils could help. Agreed that your captures so far look ok.

+1
Ð Awarded
Alex Technician
Colorado
Alex
   

Fuel pressure when cranking is 55psi if I remember correctly, same as KOEO. I'll check that when the customer brings the vehicle back.

0
Ð Awarded
Derek Educator
Virginia
Derek
 

Starting with the basics, have you changed the fuel filter? I have had the restriction in those kill fuel pumps and yes it would hold pressure. It cannot keep up with demand and exerts too much force on the fuel pump. Those filters will hold water and cause all sorts of drivability issues, people forget they are there and I have fixed many a Ford that has been shop hopping with a filter. Also…

0
Ð Awarded
Alex Technician
Colorado
Alex Update
 

Thanks everyone for the replies and for looking at my scope capture. We spoke with the customer and they do not drive the vehicle very often, so old fuel could definitely be a concern. I drained the tank and added fresh fuel, but the customer had to take the vehicle and said they would bring it back next week. I did check the fuel quality and alcohol percentage and everything looked OK. The fuel…

0
Update Ð Awarded