Injector recommendations

[brucecooner]

The weather's cooling off, and I can finally raise the hood without burning my hands then melting into a puddle of sweat.

 

So I'm wanting to put new injectors in the old 4.0 (88 Renix).

 

I've heard you can get four hole injectors that make more power.

Does that come at the cost of fuel economy?

Or are they engineered to produce better combustion so you're just using fuel more efficiently?

Or is an original spec injector still the best?

 

Also, is this a tricky operation given that you're messing with fuel delivery?

I've watched it done in a video, and at the end he had to do something to reset one of the electronic systems, which sounds like playing with fire on a persnickety old Renix.

 

Links to recommended products and tips videos are much appreciated!

[ratrapp]

i done this on my 88 when i had it.if your old injectors are in good working shape you really won't see much improvement.there really isnt anything to reset anything on the renix system if you do change the injectors.it won't hurt anything if you do upgrade the injectors.

[75sv1]

I didn't notice any improvement with the Ford 4 holes on two XJs. Both 98's. The 12 hole initially show some power improvement, for about a week. I don't k now on the newer Jeep injectors. The 4 holes seemed to run a bit smoother. I think the RENIX likes the VOLVO injectors. 

[pizzaman09]

I did the swap to the Volvo 4 hole injectors on my 90 Renix.  It was an easy swap, unbolt the fuel rail, make sure all the orings come out with the old injectors then slap the new ones in.  Some fuel will leak out but it will evaporate before you get everything buttoned back up.

The most notable change for me was a lot smoother operation.  I don't have good fuel economy or power data from before the injector swap because my header bolts were all loose and I fixed the a few days after doing injectors.

[cruiser54]

Trevor supplies rebuilt like new injectors. He can be contacted here:

trevor.skankfootracing@gmail.com

[brucecooner]

19 hours ago, cruiser54 said:

Trevor supplies rebuilt like new injectors. He can be contacted here:

trevor.skankfootracing@gmail.com

I should have mentioned that I'm not interested in more power, it's got plenty as it is.

 

Thanks cruiser (and everyone else), I'll contact Mr. Skankfoot about some.

[brucecooner]

I FINALLY got to the injector replacement this weekend.

 

At cruiser's advice, I contacted Trevor at skankfoot racing dot com. He replied to my request quickly and soon I had a new set of clean looking four holers.

Trevor said these were Bosch 700's, direct replacements for the originals.

 

 

I got thrown for a loop by the plastic bit on the end.

I was like, "I'm supposed to jam a PIECE OF PLASTIC down into the port, where gas is burning?

Won't it MELT?

 

 

They were open ended so not there for protection during shipping, and they were tightly attached, which told me it's probably supposed to remain on there.

So I did some research, apparently that is the "pintle cap" (the spritzy end of an injector is called the pintle), and it IS SUPPOSED TO BE THERE.

What I read indicate they hold the o-ring in place.

Will wonders never cease.

 

In all, removing the old injectors was not a difficult job.

I had to learn with only two trips to AutoZone that you don't need a removal tool for the older fuel lines, just pinch the plastic clip on the line and pull.

Removing the little square wire clips that hold the pigtails in place is a bit of an arm form, good thing I have a pick set.

The old fuel rail was hard to pull out after 30+ years in place, but did come free.

And man, those original injectors were groded up good.

 

 

I got the pick and picked away at the buildup in the ports, then got some carb/fuel system cleaner and went after the gunk with paper towel wrapped around a dowel and soaked with carb cleaner.

 

Rub it around, rinse, repeat until the napkin came out mostly clean.

Couldn't get it all of course, but at least the ports are clean-ish now.

I shudder to think what those cylinder heads and valves must look like though.

 

Trevor sent some "skin care petroleum jelly" with the injectors, and I knew from homework it was important to lube the rings before seating them.

The new set snapped easily into place.

 

I had taken notes on each step of the removal process, and even stuck labelled masking tape to connectors and hoses as they came off to make durn sure I got the right things back in the right places.

 

 

So re-assembly was just reversing these steps.

 

The new injectors didn't have grooves to accept the little metal clips that held the originals to the rail.

But I've read you can leave them off since the rail bolts into place.

Once the rail was bolted in place, I seated the injectors all the way down into the ports and said a little prayer that was their preferred placement.

 

Got everything re-connected and turned the key to on.

Couldn't hear the fuel pump but I put a cloth under the pressure valve and got a spritz out so it was looking good.

 

I turned it over a few times, and at this point my son noted the return fuel line at the firewall was leaking.

He got in close and found a small orange o-ring sitting on the manifold just below the line.

We inspected it and figured it must have come from the fuel line when I pulled it.  Praise the saints it hadn't disappeared into the depths.

I knew I kept that boy around for something.

So I went to pull the return line off again so we could reapply the o-ring, and I got just the briefest glimpse of ANOTHER little o-ring coming out of the end of the fitting and giving me the middle finger as it dived below the heat shield over the manifold.

I did some creative swearing and shook my fists while my son looked around back there and lo and behold he found it, thankfully it hadn't gone far.

We then noticed a little black ring still affixed to the fuel line.

He carefully inspected witness marks on the male end of the line and deduced the rings probably go on either side of the little black ring.

So we put them on in that configuration and agreed that it looked like a very proper seal.

Plugged it back up, recharged the rail, hooray this time there were no leaks.

Started it, let it warm and made sure fuel wasn't coming out anywhere.

 

The bright new yellow ones look faster, at least.

 

So we loaded up with a fire extinguisher in hand and set out for a test drive.

It did seem just a smidge peppier, though if it is it's not by much.

 

Got back home, raised the hood, and all gas seemed to still be contained within the engine.

 

So I think I'm calling it good.

Unfortunately I had to head out in a different vehicle, and didn't get to try a delayed warm start to see if that issue is fixed.

 

 

 

I do have one more question though.

 

I've never used loctite or any other sort of thread management chemicals. 

I noticed the fuel rail bolrts broke with a clank that sounded distinctly engineered in nature, and they had a silvery substance on them.

It seems somebody had put something on there.

 

Do I need to get a substance on the fuel rail bolt threads to keep them locked in place?

I'm sure they have  a torque rating, do I need to be sure and get them just so?

I snugged them up pretty well, but not overly so, will that be sufficient? 

(I do plan to check them after a few more miles)

 

 

Anyway, big thanks to cruiser and the CC crew for the help!

 

 

[cruiser54]

The rail bolts are fine. 

Those are steel bolts in aluminum.

There is a chemical reaction between the dissimilar metals. Hence the POP. 

 

And just for fun, here's the injector wiring diagram

 

 

[brucecooner]

It's been cold starting and running pretty well. 

I'd been taking it out to run errands to see if the hot start issue was still there.

If I go in a store for a few, come back within 10-15 minutes it'll start.

 

But I stopped at the local burger joint long enough to eat the other day, and when I got back in got the difficult start again.

Cranked for a few seconds, didn't want to start.

It did start, just not as peppy a fireup as I'd gotten used to.

 

So injectors didn't fix it, but they needed replacing anyway so it was a good idea.

But I guess there's still something to look for.

 

Given that it takes a chunk of time (30-45 minutes) for it to display this behavior, does that point to anything in particular?

 

I've heard the 4.0's sitting will vaporize fuel in the rail, and some guys swear wraparound foil heat shielding on the rail fixes it, but I would think if that was the problem my short stops at the store would have been enough to produce the problem.

 

I do plan to perform cruiser's fuel pump tips soon.

 

[cruiser54]

Renix doesn't heat soak like the later models. 

 

[brucecooner]

On 11/10/2022 at 9:09 PM, cruiser54 said:

Renix doesn't heat soak like the later models. 

 

Would a Renix have the CPS issue? 

I've heard heat soak of the CPS can cause hard starts.

I imagine, however, that would occur when you attempt any warm start, and I don't get that.

It has to sit for a while to get the difficult start.

 

Another culprit could be some longer term effect in the fuel system, but that's a guess at this point.

[cruiser54]

Remind me, have you completed Tips 1 through 5 yourself? 

[brucecooner]

On 11/13/2022 at 6:15 AM, cruiser54 said:

Remind me, have you completed Tips 1 through 5 yourself? 

I am going through them as I have time.

I've gotten the first one, cleaned up the grounds down on the block.

And I've pulled out the relays and cleaned them up.

Wanting to get the fuel pump ones next.

 

I haven't gone near the C101, yet, I can sense that if I so much as wiggle that thing the engine will stop running, so I'll have to take it by surprise one day.

 

[cruiser54]

You won't make the C101 worse. Or anything else by refreshing it. 

Tips 1 through 5 can be done in under an hour easily.