I wanted to share this great video on fuel delivery, but specifically testing fuel pumps at the fuel pump relay (or right at the fuel pump for the XJ) with a low current DC clamp and an oscilloscope. Tons of videos on using the cheaper 2 channel Pico scope that I’m still getting a handle on.
The video discusses how to check/calculate rpm and armature/brushes checks.
And haven’t watched the fuel injector portion yet.
Could help someone with a fuel pump that seems to be ok but could be on the way out electrically.
(51) 8 Fuel Delivery Diagnostics - YouTube
The simplest pump test is to connect a fuel pressure gauge directly to the inlet hose at the fuel rail, jdere…
‘Perfect’ pumps deliver 100+ psi, ‘good enough’ deliver 60 - 70 psi - below 40 psi; the pump will not run the engine effectively. There is no need for more complicated testing for ‘why’; just replace a bad pump, and accept ‘good enough’ as working…
xj6 85 Sov Europe (UK/NZ)
Your absolutely correct that checking fuel pressure at the fuel rail is the simplest test to do. I just wanted to point forum members to some of the latest testing methods and technology. If someone has more than one vehicle, a low amp probe and an inexpensive oscilloscope could help them diagnose fuel pumps and ignition components efficiently.
6 months ago I had a fuel pump issue with my 10 year old Chevy Express Van. Drove me absolutely nuts. Talk about parts cannon. I had to throw everything at it.
Van wouldn’t start, but then would, checked fuel pressure, it was fine, then stalled out so I replaced fuel pump, still issues, replaced fuse box, fine for 2 months, then no start again. Finally replaced the connector since one wire had a burn mark at the terminal. Huge pain since fuel pump was in the tank. I believe I could have found the issue faster with the low amp probe as shown in the video I posted.
I remember a forum member named Sean Straw mentioning oscilloscope testing all the time but I didn’t know how to use or know where to get the info. Now tons of utube videos on how to use and what to buy inexpensively compared to the past.
Thanks for all your help!