How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
Type Your Chevy Question Here...
GM Tech (Cam) is online now
A new question is answered every 9 seconds

I just swapped engine in 98 k35 pu. Upgraded to mpfi. Can't

Customer Question

I just swapped engine in 98 k35 pu. Upgraded to mpfi. Can't get truck to start. Weird part is that if you step on the throttle while cranking, fuel pump runs indefinitely even after ignition is turned off. Any ideas?
Submitted: 1 year ago.
Category: Chevy
Expert:  Tool Hut replied 1 year ago.

Hi, My Name is ***** ***** for posting your question to just answer. I am a independent contractor for just answer, and ASE Certified Master Auto Technician with 20 years experience. I am confident we can resolve your problem together.Please remember I don't know your skill level. I can't see, smell, hear, or touch the vehicle. It may take a few back and forth replies to get to a satisfactory resolution.There will probably be some equipment needed for a proper diagnosis. If you are not comfortable with this or do not have any test equipment please let me know ASAP. I also try to give all of the information you may need expecting a positive rating. I am not compensated for my time until you leave a positive rating. Your rating should be based on the service you received.

What brand of MPFI? What is your fuel pressure?

Customer: replied 1 year ago.
It is an AC Delco retrofit fuel injection. If you are familiar with this particular model, you will know that the factory oem unit was a SCFI, commonly called a "spider" that was prone to problems. This was a Chevy recommended upgrade. For more background, old engine seized up due to broken oil line. Replacement motor is a gm certified L31 crate motor. Swap went well with no obvious hitches. As for my skill level, I would say medium. I have performed several engine swaps in my life, but none with fuel injection. Have done many repairs to several of these vortec motors. I am also armed with gm shop manual and know how to read. The entire swap was done "by the book". I do not have fuel pressure reading as of yet, but by the sound of fuel running through system, it seems high. This is a hobby project and I will be unable get you an actual pressure until Sunday, but I do have the proper guage.
Expert:  Tool Hut replied 1 year ago.

The CPI or SFCI is very critical for fuel pressure. Did the kit come with a pump?

Expert:  Tool Hut replied 1 year ago.

The CPI unit has a minimum fuel pressure of 55PSI and typically wont start at 50PSI

Customer: replied 1 year ago.
I have a steady 60 psi fuel pressure. Also checked timing setup and all seems good, not 180 dog off. Definitely have spark though.
Expert:  Tool Hut replied 1 year ago.

I assume it came with a distributor. Are you confident it is triggering injector?

Customer: replied 1 year ago.
How do I check?
Expert:  Tool Hut replied 1 year ago.

A test light would be easiest. Do you have the wiring schematic that came with engine? If not I can get an idea from a CPI engine. How many wires hook to injector?