lvcherokee

I have a 1987 4.0l Renix. Thought I was buying 703 injectors, but received 746's (0280155746). 125,000 miles, stock intake and engine, nothing fancy. Just looking for better idle, a little pep, and maybe mileage...

Will these injectors work?

Thanks!!

racebum

is it this injector?

http://fuelinjectorconnection.com/sh...?productid=276

if so this is a 19lb/hr injector which is correct for your application. the 703s are too large for a pre 91 cherokee. i know guys have used them but their proper fit is 91-95 which they flow nearly identical to. {i have read, still waiting to do an actual flow test on one and or find hard data of someone who has done one, bosch oddly rates them at 16.75lb/hr however all the tests i have read about show roughly 21.5lb/hr@40psi}

i'm not so sure about their advice on working 87-95, 87-90 would be more like it. the 91-95 cherokee used a 21lb injector at 39psi. where as 87-90 is 18.6lb/hr

one of the better injector threads i have came across is http://www.jeepforum.com/forum/f13/d...36/index5.html

NorCalJeep

703s dont increase gas mileage, only idle. The only reason it might have increased you mileage is your previous injectors were dirty.

lvcherokee

That fuelinjectorconnection.com site sure looks like the one I bought, and they are listed at 19lb/hr, so I will give them a shot.
thanks for the advice!
If they are not the right ones, what kind of symptoms should we look for?

salad

Running too rich (engine slow to warm, raw gas smell, using too much fuel), running too lean (overheating or up to temp abnormally fast), and leaks on the intake manifold, which could cause a fire under the hood. I suppose maybe a high idle due to vacuum leak from the action end not seating properly, but I'd image that if they didn't fit it would cause a problem at both ends.

DFlintstone

The 703's flow a little more, but when it's warmed up the 02 sensor "trims" it to the proper mix. People pass smog with them in their Renix Jeeps. Jeep runs great, fantastic throttle response and nice idle. My thinking though is there is a problem....while it's cold, before the 02 does it's magic the ECU uses a "default pulse width", for 18.6 Lbs/Hr. The 703's being higher makes it run rich, get crap mileage there, AND take a little longer to warm up being so rich. That's my thinking anyway. I'm looking to sell my, (8), (got 2 extra), 703's and go to 4 hole 18-19# injectors for my Renix.

Oh Ha! I now recognize from the search results you are the same guy from last week. Yea. Volvo injectors. The only reference I found was 23-24 Lbs/hr. I'm not sure that's correct though.

racebum

correct, warm at part throttle the 703s will function properly in this application. it's when cold and at WOT when the ecu is either at open loop or switches there during heavy throttle that you go to a fixed map and the ecu ignores the o2. this is bad for a few reasons.

1. you use more fuel
2. you're down on hp being too rich
3. you burn out your cat with excess gas in the exhaust
4. potential for ringwash
5. potential for deposits on exhaust valves and spark plugs

there are some pretty slick deals on 19lb injectors listed on ebay right now

http://www.ebay.com/itm/Ford-Motorsp...#ht_994wt_1163

is one example

if i could find a cheap adj fuel pressure regulator {that works} for my 94 i would use these too

DFlintstone

Good point ^^, I hadn't even thought of WOT...not that I go over 70/80% often.


Your right! ^^$50...I ended up spending more, (a tad) on my 703's at the JY!

DFlintstone

Idk...I'm just learning here myself. I think they went to the higher pressure partly to shoot for better atomization. Also there is less chance the fuel is gonna boil at the higher pressure. Assuming the 92 uses the higher rate I wonder if 703's might be a good match for you. I'm not going to look into those details until I get my OWN straight!

racebum

my 94 is at the same pressure you are, 39psi, it just uses a 21lb/hr injector vs your 18.6lb,

you know what, you just made me think about something. if i swiped a late 49psi fuel rail i could use 19lb injectors as they would be right at 21.3lb/hr@49psi and i would have the benefits of higher pressure

i can't remember when the 49psi started but it was either 96 or a year or two after. right in the start of the obd2 days. i know there's a chart somewhere online

DFlintstone

There's some stuff here> http://www.jeep4.0performance.4mg.com/tech_specs.html

lvcherokee

thanks, that is good info!
the 746's sound like they will do the trick, will give 'em a shot.