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Dr. Hamman
Dr. Hamman, Automotive Engineer
Category: Car
Satisfied Customers: 6286
Experience:  30 years experience, Repairing, building, & designing, automobiles.
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87 ford ranger: 12v..,,same sensor..air intake..neg batt

Resolved Question:

I have an 87 ford ranger 2.9 F.I. A while ago i had a problem with the EMU. I had experienced a sever voltage drop at the pin that supplies 12v to the fuel pump and the
injectors i was getting about 5.5-6 vdc..I replaced the box..problem fixed truck runs great..
six months later ,,,,same problem,,,box is under warranty...take it back,,,get another one
(remanufactured of course) and off I go....three weeks later..same problem,,,,I replace the map sensor and check the vacuum lines that attach to the fitting at the air intake..alll good..check the integrity of the ground between the box plug and the neg batt cable
(unattached from the battery) and no sweat, .6 ohms the box is grounded properly..Am I just getting bad it a notorious problem or is there some underlying reason that these boxes are going bad on me? should I search out an N.O.S. unit?
According to the schematic the voltage goes right through the box to the fuel injectors
and the fuel pump..So why would I have a momentary voltage drop that makes the truck
cut out? Eventually the voltage drop turns into a permanent situation and the truck wont
start...Until I replace the box....What Gives....Any Idea?
Submitted: 6 years ago.
Category: Car
Expert:  al-mod replied 6 years ago.

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Customer: replied 6 years ago.
what do you need to know? I will be glad to clarify any portion of the question that seems to be ambiguous or unclear.
Expert:  Dr. Hamman replied 6 years ago.
Hi, I will do my best to assist you. When you are finished please click on accept. I don't get paid unless you do. I don't know if you are a pro or a novice so we may have to fine tune the answer. I only know as much about your problem as you have told me in your post, so my answer will be based on what you have posted. Feel free to add any additional info you feel is needed.

I would suspect that you have an intermittent problem causing excessive amperage draw, and the box is getting overloaded, and eventually quits. This type of problem is tough to find if it is intermittent, it’s a lot harder. You could place an ammeter in series with this circuit to check and see what the amperage draw is. Also you should look into the stock resistance for the fuel injectors, and individually measure the resistance of the injectors. There are various impedance injectors that will bolt in, and will cause this type of problem. If replacement injectors have been installed that were a lower resistance, they will draw more amperage, and this in time could burn out the box. Check all this out and inspect the wiring in the circuits that are attached to this power source, you may have an intermittent short, burning out the box. Good luck, and Thanks for using Just Answer.

I hope this helps, 100% satisfaction is my goal. If the answer is not clear, please reply and I will assist you more. When you're satisfied, click on accept. I don't get paid unless you do. A bonus and positive feedback are always appreciated, good luck and Thanks.
Dr. Hamman, Automotive Engineer
Category: Car
Satisfied Customers: 6286
Experience: 30 years experience, Repairing, building, & designing, automobiles.
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