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1991 Ford Ranger 4.0 V6. Replaced fuel injectors with

1991 Ford Ranger 4.0...

1991 Ford Ranger 4.0 V6. Replaced fuel injectors with upgraded 24 Lbs injectors. Truck will turn over will not start. Do I need to do anything to re-calibrate these injectors?

Mechanic's Assistant: Has the vehicle turned into a gas hog? And how does it start -- same as usual?

Will not start. Will turn over but not start.

Mechanic's Assistant: Are you fixing your Ranger yourself? What have you tried so far?

Yes. nothing at this point.

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Answered in 14 minutes by:
5/30/2018
Matt
Matt, Engineer
Category: Ford
Satisfied Customers: 23,457
Experience: BEng hons Mech engineering, in auto industry 22 years
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Hello and welcome to Just Answer

If you've replaced the stock injectors with a part that flows more then yes you definitely need to re-calibrate the ECU to accommodate them otherwise the fuel mix will run very rich all the time

why did you uprate the injectors? are you planning to fit a supercharger?

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Customer reply replied 2 months ago
No, simply the most cost effective solution. Here is what I purchased "Bosch-Upgrade-4-Hole-Ranger-Aerostar-Explorer-4-0L-91-95-Fuel-Injector-Set". They are compatible with the 1991 Ranger as well. How do I re-calibrate the ECU?

Ok according to my info the stock injector is a 19lb / hr part so by going to 24lb/hr you've increased the fuelling by 21%

so you can either locate a tuning shop that can recalibrate the ECU or purchase the parts to do it yourself

see here

https://www.cjponyparts.com/mustang-computers-programmers/c/60060270/?product_year_mustang=690

however I'd say the best andd cheapest route is to just replace the injectors with the correct flow rate part

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Hi
do you still need help?
Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! If you're not pleased, also let me know because rating bad does not result in a refund, there are better options. Rating now will not close this post nor prevent further replies
Thanks Matt

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Customer reply replied 2 months ago
OK I have done more research and pulled out the replacement injectors I installed, to see actual part number. The replacement injector is a Bosch 0-280-150-943 and all of the specs I can find are identical to the original part number 0-280-150-766 except the Ohms. I was mistaken when I thought they were a higher flow rate. The 943 part requires 14.3 Ohms and the original part 766 requires 15.5 Ohms. Does this difference require a ECM reprogramming? The flow rates are the same. If it does not then I still have the same problem--motor turns over strongly, but it will not "catch". Produces excessive white smoke that has a smell of unburnt gasoline. I only have water in the radiator right now so it is not antifreeze being burnt.

the slightly lower resistance will alter the fuelling but only by small amount and not enough to stop it starting

lets go back to basics a little

1st check for spark by removing one of the spark plugs and plug it back into its lead and rest it on the metal of the engine ( DO NOT hold it on place by hand) then have your assistant turn the engine over whilst you watch the plug. It should give a fat blue spark at regular intervals.

If not then check that there's power to the coil pack (at the other end of the plug lead) using a meter. If there’s 12V at the pack but no spark then check the ECU power supply (fuse and relay) and also the connections to the crankshaft speed sensor.

If this is OK then check if the car will start using a squirt of quick/ easi start into the intake then this confirms the problem is lack of fuel

Matt
Matt, Engineer
Category: Ford
Satisfied Customers: 23,457
Experience: BEng hons Mech engineering, in auto industry 22 years
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Customer reply replied 1 month ago
If you can see the previous thread it would save us both work. Essentials - 1991 Ford Ranger 4.0 V6, replaced fuel injectors with slightly different model (only difference is original injectors (PN 0-280-150-766) operated at 15.5 Ohms and the replacement injectors (PN 0-280-150-943) operate at 14.3 Ohms). Vehicle will turnover, but will not start. I have checked spark (it is good), checked the crankshaft speed connector (it appears fine), used starting fluid engine did not start (all of this was previously suggested in another thread). The engine does turnover well, I do think I am hearing some backfiring, and getting white exhaust fumes that smell like gas (it is not anti-freeze none in truck at the moment only water). So I am stumped any suggestions would be appreciated.

Hello

as you have spark but it won't go on starting fluid then I'd next do a compression test across all cylinders as if the cam timing is out then you'll have high and low readings ( they should all be within 10-15 psi of each other)

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Customer reply replied 1 month ago
Isn't there an easier way to check my timing if you believe that is the issue? I didn't do anything that should have impacted the compression.

well you can lift the valve covers to check if the timing marks all line up ?

but to be honest doing a compression test is probably less work

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plus checking compression also shows if the engine is in good health too

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Customer reply replied 1 month ago
OK Thank You.
Customer reply replied 1 month ago
Matt, Here are the results of the compression test. All in PSI cylinders 1-150; 2-155; 3-155; 4-155; 5-149; 6-155 according to my research this engine specs are--all cylinders > 100 PSI and no difference > 75 PSI between any two cylinders so my quick take on this is that the compression is within range. Any other suggestions. Thanks

Ok thats a good set of numbers and shows the cam timing is correct and the engine is basically healthy

looking back through the previous Q & A , I don't see any signs of having checked fuel pressure? as if the fuel pressure is too high then it'l be over-fuelling

and its not unknown for the pressure regulators to fail

it should be 45psi or therabouts

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Customer reply replied 1 month ago
Ok, I was able to check the fuel pressure. With the key only on (cycled several times as the instructions said) the static pressure was 37 PSI specs call for 40 PSI. When I cranked the engine the pressure went up to 40 PSI the repair manual and the pressure gauge users guide both said it should fall when the engine is running. Since I can't get it to start, I had a person continuously crank it to simulate an idle. I did replace the fuel regulator with a new one. I suppose it could have been bad new or the vacuum tube could be bad. Your thoughts? suggestions on next steps.
Customer reply replied 1 month ago
both said that at idle the gauge should fall 3-10 psi.

Hello

that fuel pressure sounds fine

do you still have the original injectors to try?

if so then it'd worthwhile putting them back in as an experiment

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Customer reply replied 29 days ago
I do. I will give it a try. It will be several days before I can. I will let you know what happens.

understood

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Customer reply replied 18 days ago
I put the original injectors back in (I put new seals, spacers, and nozzle covers on them). I checked the injectors' spray pattern and it seemed fine. I also checked the resistance on each one and they were all within .1 ohms of each other (16.0-16.1). Same results--engine will turn over and is strong, It just doesn't seem to want to "catch". any further trouble shooting steps would be appreciated.

OK next thing to check is the ignition lead firing order onto the coil pack

I've attached the correct firing order and lead order, so thats well worth checking

also check the injector loom is connected to the correct injectors too as if its firing out of order this too will prevent a start

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