89 B2 2.9 4x4 hard to start and rough under load

[Jmthunderbird]

hello all, first id like to say thanks for your collective knowledge on this site. i have searched, but i haven't really found a problem similar to mine.

in the mornings, its hard to start. VERY hard. it takes 5 or 6 tries of 15-20 seconds of cranking. once it starts, though, it idles like a sewing machine (just adjusted the valves and did a tune up). driving normal, it runs great, but under full load, it has a bit of a stumble. sometimes it there, sometimes its not. it will pull real well for a few RPM's, then back off like you let up on the pedal some, then it pulls again. it get worse in lower gears. i suspected fuel pressure, so i hooked my gauge up, i get 35 at idle, then as i accelerate, i get 38 at 2000, 35 at 3000, 32 at 4000 and 30 at 5000. it slowly drops as rpms go up. im used to turbo cars, with pressure going up with boost, and down with vacuum, so this has me stumped... do my readings seem correct, or do i have a fuel system problem?

also, id like to know how many pumps i have, and how many filters i have on an 89 B2 4x4. ive seen mention of dual pumps and dual filters on the rangers, wasnt sure if the B2 had the same thing?

thanks guys!

-J0N

edit- i tried a few things that other members tried, with no change. i tried starting it with the IAC unplugged, took just as long, and still wouldn't idle. tried with TPS unplugged, and it wouldn't start at all.

i have now added a new air filter to this list of things i changed. no real change in starting.

-J

 

[Jmthunderbird]

more-a new fuel filter helped a LOT. well know tomorrow morning if it starts better, as it was already warm when i changed it. there's still a low end miss at 2-3k, im wondering if cleaning and gapping the plugs isn't good enough, maybe i just need new ones.

-J0N

 

[hopster]

pull the vacuum line off the fuel pressure regulator if fuel comes out of the line replace the fpr

 

[Jmthunderbird]

checked it. no fuel in the line or the nipple (hehe i said nipple) of the reg. it seems ok.

by the way, now that i have changed the fuel filter, the truck runs better, but the fuel pressure readings are close to the same. it doesnt start any easier...still hard to start when cold.

still has a stumble from 2-3k...

-J0N

 

[Jmthunderbird]

anyone? i cant seem to got this to run right. once its warm it ok, but cold start is horrid, and it ALWAYS has a stumble in it from 2-3k.
plugs? all other tune up stuff is new...plugs were just ohmed to be 1.0, cleaned and regapped to .039. can they still be bad if the ohm good and are clean?

-J0N

 

[bluelight2]

Same problem

I hv same problem. i wanna know how many pumps i have, and how many filters i have on an 89 B2 4x4.

 

[Shran]

Your fuel pressure readings sound about right. 30 at idle and around 40 when you crack the throttle is spec.

You could try new plugs...if they are fouled then you will get little to no spark. I've had a few that didn't really look fouled but wouldn't spark.

Could be a weak or dead low pressure fuel pump (the one in the tank) - had that issue before... fuel pressure looked fine but the pump was totally dead.

 

[Jmthunderbird]

so i do have two pumps? how silly...

-J0N

 

[Shran]

Yup... some 89s and some 90s have just one in the tank... just don't ever buy an '86+ full size truck with dual tanks or first gen Ranger with dual tanks... they have three pumps... dropping a bunch of coin on three new pumps in the same day sucks, been there, done that.

 

[Jmthunderbird]

it seems i have one.

i dropped the tank, fixed some faulty fuel lines, checked the pump, and put it all back together. now i have 20-25 psi of fuel pressure. it just flat runs horrible. the pump is good, bench tested it to 60psi. all the lines by the pump have been replaced with factory stuff. everything seems fine there, but it still dont run. am i looking at a bad regulator here? my pressure gauge has a long rubber hose on it, and it pulses when its idling. pressure never goes above 30-32 now. 25 or lower when driving. what the hell am i missing? when i disconnect the line from the reg (vacuum) the pressure doesnt change, is this right?

-J0N

 

[Shran]

What process did you use to bench test the fuel pump?

Kind of sounds like a bad regulator to me, although you didn't touch it when you removed the fuel pump and fixed the lines, I'm assuming. Bad regulators usually have an unusually high pressure reading too. Did you get a good look inside the tank? If it is dirty enough to clog the filter the first time, it could have happened again. Try removing the filter, draining it, and see if you can blow air through it.

 

[feellnfroggy]

Does this year of ranger have a mAF? it sounds more like an emissions problem than fuel problem. Im thinkin bad MAF.

 

[Shran]

No, 99% of 2.9s are speed density. Supposedly SOME of the very last ones produced (we are talking like '91 or '92 here) had speed density because of California emissions requirements but they are rare.

 

[Jmthunderbird]

i pulled the tank again, and bench tested the pump. again. basically, i hook it directly to the lines going into the frame rail, and turn it on. instant 40 psi. so i took a harder look at the pump mount and hanger, and found my problem. the silly little pressure valve/diaphragm on the top of the pump where the nozzle goes in was malfunctioning. i tried to fix it, but taking it apart only yielded more broken parts. so i threw in the towel, and even though the pump is fine, i bough a whole new assembly for $150. popped it in, BAM, runs perfect. 38 at idle, 35-45 under normal cruising, and runs very well. good power too (im actually impressed by this bone stock 2.9 with 2 cats, 2 mufflers, a dirty air filter, old ass plugs, and 177k).

anyways, next is some minor lift (blocks under stock springs, blocks under stock shackles), and a new exhaust. ill also be adding more lighting, pipe bumpers, a snorkel, roof rack, 31's, some steel wheels with less backspacing to make the track wider, and some minor power mods, like better plugs and a bigger TB.

thanks for the help guys, ill be in next week with questions on how to replace this useless CV shaft for a real drive shaft.

-J0N

 

[Louisville86]

Glad you got it fixed; fuel problems can be tricky.