Rebuild, Replace or Risk It?

Time for a game. I'm rebuilding a Mazda BP-4W ('00 Miata engine). Said engine appears to have been rebuilt in the past, never/barely run, and then sat for an indeterminate amount of time (top was all crumbly like they get and interior was disintegrated). The engine also had the #1 spark plug out and the hood was missing, filling #1 up with water.

Now, I plan on having the block machined/bored/yada yada yada. My concern is the fuel injectors. I don't know when the last time this engine ran or how long it sat in the elements. And the injectors require removing the intake manifold, which looks like it'd be a real treat with the engine in the car.

Should I just replace them, or send them out and have them checked/rebuilt (if so, who does the hive recommend?), or just risk them? I'm not a strong proponent of the last one for fear of one hanging open or closed and at the best, having to change them in the car, at the worst blowing up my new engine. I'm also on a bit of a time crunch, as I have about 3 months to get the engine machined, assembled and swapped into my '90 Miata.

Thanks, in advance.

I've never heard of the intake manifold being removed to get at the injectors. Is it just the top half of the intake that needs to be removed?

Oh right, I forgot the intake manifold splits in half. Still rather not have to do that.

Send them out and/or pluck another set from the junk yard.

Why put all that effort into redoing just to massively cut a corner on the fuel system.

Was in the same situation with a subaru a while back. Sort of questioned the history of the injectors I was about to use. Sent them to RC engineering. Glad I did as one of them flowed noticeably less than the other three before cleaning. After cleaning they were all very close in flow.

Of course you'll have to balance the cost of cleaning vs cost of replacements. I dont have any experience with miata injectors but the subaru ones I needed were $$$ so the cost of cleaning was an easy decision.

In reply to HappyAndy:

Junkyard isn't an option, as Miatae tend to be scarce around here (CNY area). Like I said, the "Risk It" option was certainly my least preferred option

In reply to appliance_racer:

Rock Auto lists 3 different new injectors for my car. The Ultra Power is $23.79, Standard Motor Products is $90.89 and the AirTex/Wells is $187.79. Quite a large spread

Yeah, pulling the injectors out is easy.

I suspect the injectors are probably fine, if you're really concerned, then send them out to be cleaned/inspected. I'd rather have cleaned & certified Mazda OEM injectors than $24 random aftermarket ones.

WitchHunter tests and refurbs units for $22 each. Seems cheap enough to just do.

I wouldn't touch an aftermarket "rebuilt" injector with a 10 foot pole. Nobody ever changes injectors just for grins, and many bad ones will pass a cold test. Therefore, you have to hope you are buying an injector that somebody mis-diagnosed and changed instead of fixing the real problem.

Send yours out, or buy new ones from a Mazda box.

In reply to Streetwiseguy: The ones I priced were listed as new, not rebuilt. I didn't even look at the rebuilt ones on Rock Auto.

Injectors are almost a non-wear item. Clean the outsides

Pull the screens out of the inlets, hose them out with carb spray.

Trigger the injector with a 9v battery and blow air through them backwards and forwards.

Clean or replace the screens on the inlet and test.

The test part is tricky, can be done with a megasquirt

Or you can just send them out, better to send out 2 sets so you can get a matched set back.

I've used cruzin performance before for cleaning. I was quite happy with the price and the before/after data.

They were out of Michigan, I believe. The round trip was about a week from pa at the time.

Streetwiseguy wrote: I wouldn't touch an aftermarket "rebuilt" injector with a 10 foot pole. Nobody ever changes injectors just for grins, and many bad ones will pass a cold test. Therefore, you have to hope you are buying an injector that somebody mis-diagnosed and changed instead of fixing the real problem. Send yours out, or buy new ones from a Mazda box.

Or buy used OEM. Junkyard injectors are probably fine, as are pull-outs from someone who wanted id1000s for their EFR turbo build. :)

Are you sticking with gas build or do you have E-85 plans? If the latter I've heard you want to get RX-8 injectors and a higher performance fuel pump.

I have some MSM injectors you can have if I can find them. They were fine when they were on the car but they have been sitting for a few years.

In reply to KyAllroad:

Nope, no E-85. I think that E-85 is a pain in the butt, and no one sells it around here either. I typically run ethanol-free 93.

In reply to EvanB: The plan is to run it on the stock '90 ECU, so I'd rather just run the stock injectors for this engine. I'm assuming that the MSM had higher flow injectors.

That is quite a spread in price. IIRC I spent $35 per injector for the cleaning service. Was about 5 day turn around. IMO just send yours out for peace of mind. I also like the idea of sending out two sets to get a matched set back if you can source another 4 relatively easy.

NickD wrote: In reply to KyAllroad: Nope, no E-85. I think that E-85 is a pain in the butt, and no one sells it around here either. I typically run ethanol-free 93. In reply to EvanB: The plan is to run it on the stock '90 ECU, so I'd rather just run the stock injectors for this engine. I'm assuming that the MSM had higher flow injectors.

They are ~260cc I believe, not much larger than the stock bp4w injectors.

EvanB wrote:

NickD wrote: In reply to KyAllroad: Nope, no E-85. I think that E-85 is a pain in the butt, and no one sells it around here either. I typically run ethanol-free 93. In reply to EvanB: The plan is to run it on the stock '90 ECU, so I'd rather just run the stock injectors for this engine. I'm assuming that the MSM had higher flow injectors.

They are ~260cc I believe, not much larger than the stock bp4w injectors.

Yup, looks like they are 260cc at the nominal 43.5psi of pule pressure, compared to the BP-4Ws 240cc at 43.5psi. Which considering my engine will end up with an overbore, header, high-flow cat, exhaust and BP-5A/Mazdaspeed camshaft, might just work out in my favor.

In reply to NickD:

If you want to give them a shot I will try to dig them out of the garage this weekend.

Sure, sounds good. Thanks, man.

NickD wrote: Yup, looks like they are 260cc at the nominal 43.5psi of pule pressure, compared to the BP-4Ws 240cc at 43.5psi. Which considering my engine will end up with an overbore, header, high-flow cat, exhaust and BP-5A/Mazdaspeed camshaft, might just work out in my favor.

If you're planning to run the stock ECU, you're best off running the stock BP-4W injectors.

codrus wrote:

NickD wrote: Yup, looks like they are 260cc at the nominal 43.5psi of pule pressure, compared to the BP-4Ws 240cc at 43.5psi. Which considering my engine will end up with an overbore, header, high-flow cat, exhaust and BP-5A/Mazdaspeed camshaft, might just work out in my favor.

If you're planning to run the stock ECU, you're best off running the stock BP-4W injectors.

Yeah? Care to explain?