dt3257

I have a 1989 928s4. I believe the fuel injectors are my issues after previous posts and following closely to what is said here. The cars starts awesome cold, starts OK if left for 5 minutes or less and starts very poorly if left for anything longer than 5 minutes. I believe the injector or injectors are leaking back because you have to put it to the mat to start it when warm.

My question is....is it worth it to try clean or repair the in injector or injectors, or is it wise just to buy a new set and replace them all just because of the age of the car.

davek9

Before doing an Injector job, did you verify that all the sensors are working, Temp(s) and WOT ?
The computer may not know the eng is hot.

Injectors can not be repaired or tuned, only cleaned and matched with other like injectors, usualy need to provide more than 8 to whoever is doing the cleaning & testing ~ $125 usd for 8

A new set will run around 300 bucks ???

John Speake

A good test of injector leakage is to do the leakdown fuel pressure test.

I would suspect some other problem, like O2 sensor, etc, before pulling out the injectors without any idea of whether they are the problem

Do like Davek9 suggests, check the easy stuff first, like temp sensor 2.

Do a search on "running rich" for hints.

WallyP

First thing to check would be the diaphragms in the fuel rail dampeners and pressure regulator. Find these three units, then pull the little rubber vacuum line on each and check for any traces of fuel in the vacuum line. Any leaking unit should be replaced.

If that is not the problem, move on to the Temp II sensor as suggested.

Injectors are a possible but much less likely source of your problem...

Bill Ball

I agree you are describing a classic leaky injector starting trouble pattern. If it were the temp II sensor, it would be hard to restart warm, whether it sat for a few seconds or 30 minutes. Same with a defective dampner. You have a different pattern of behavior that fits with leaky injector(s) flooding cylinder(s).

Still, for completeness, it's easy to check the temp II sensor for proper resistance to ground versus temperature and look for fuel in the dampner vacuum lines.

You can verify that it is leaky injecters by measuring fuel pressure at the rail. You squeeze clamp the fuel return line and briefly activate the fuel pump by jumpering the fuel pressure relay socket pins 30-87 to build pressure. Just take a few seconds. Then if the pressure drops over the next few minutes, and you don't find fuel in the dampner vacuum lines, you have leaky injectors.

Replacement Bosch/Ford 19 lb injectors used to be avilable for about $200 per 8, although you would need to get the proper larger lower o-rings as well (Roger sells them). I can't find them for sale online anywhere at the moment - maybe they have been D/C'd. The newer 4-port style are around $300+. Maybe someone has a better source:
http://www.fiveomotorsport.com/product-search/?v=19296

Cleaning may or may not resolve leaky injectors, but it runs bare minimum $120.
http://www.witchhunter.com/

StratfordShark

The original poster has a 1989 S4. Service Info for this MY stresses that the rubber fuel hoses have been replaced by polyamide versions which can be damaged if clamped. The exception is hose from tank to pump.

The info publication recommends change to leakdown test so that return line isn't clamped. Instead it says that once you verify that pressure loss is abnormal, raise pressure again as Bill describes, then clamp at the tank/pump hose. If pressure drop is abnormal (>0.5bar in 30 mins hot engine) tehn the injectors are leaky. If pressure drop normal then the check valve is faulty.

I got this from Service Information S4 MY89.

Bill Ball

Hmmm... I'm aware of the change to the polyamid U between the FPR and the dampner, but the return line from the regulator that fastens to the fuel cooler looks like rubber to me. It would be very unusual for that line to be polyamid since this is a very low pressure line. Regardless, I don't use that line for this test - it's too hard to get to. I use the fuel return hose at the tank, which is still rubber. Mine is shown here. BUT, the bulletin makes a point I forgot to mention - you need to clamp the feed or otherwise verify that the check valve is working too. They suggest pulling the return line to verify no flow out of the regulator rather than clamping the return line. In general troubleshooting that would be a good idea in order to verify that the regulator isn't leaking, but for the purposes of ruling out the injectors, you can clamp the return line at the tank as an alternative. Thanks.

dt3257

Yes Bill, I do believe it is the injectors just because of the symtoms. I will try that test on the injectors and see what happens, if not I guess it will be time to start looking at some of these other culprits listed. Thanks Guys.

StratfordShark

In that case I was wrong Bill and thanks for this info.

That's actually the point where I would usually clamp the return line. I hadn't even considered that it may still be rubber as the service info only refers to the tank/pump line being rubber.

Useful to know I can still clamp here if necessary as it is handy as you say.

Anyway my FP OK or at least no warm start problems (I have a FP gauge from my old car but not used it on current S4). The symptoms described by original poster though were exactly the ones I had which were fixed with new set of injectors (single hole Fords from Summit Racing), after verifying injectors leaking using the pre-Polyamide leakdown test instructions (the car was my previous MY88).

Bill Ball

I was surprised too to read the 89 warm start troubleshooting guide in the MY service technique. It refers directly to the return line out of the regulator as being changed to polyamid, just as you said. Makes no real sense, but normally I would take that as gospel too. There are a few ways you could do this test, all of them slightly cumbersome.

tveltman

FWIW, I just got a set of rebuilt 24# injectors from roger for something like 260

Larry Velk

My '86 is smoother between 1 000, and 2 000, rpm with the 4-hole injectors. This difference is notable if compared to the 60k originals (not imaginary).

dt3257

so where's the best/cheapest place to get a set if that ends up being my issue??

Bill Ball

Well, that one link I found has the newer 4 hole type for $329 and it appears they come with the correct larger bottom o-rings as well.
http://www.fiveomotorsport.com/product-search/?v=19296

Here is the stock equivalent 1-hole type for cheap. These should work fine, but you will need to buy the correct 16.5mm lower o-ring. Roger probably still sell them for $20 for 8.

http://cgi.ebay.com/ebaymotors/FORD-...item439320c419

FredR

Cleaning/servicing fuel injectors seems to be one of the biggest neglect areas. The test rig clearly shows how much injector performance is off. I was surprised to find such a rig out here and when we tested the injectors I was down about 7% in terms of total fuel injected with one injector being about 15% out. Leaky injectors just add to the problems.

for reasons I cannot explain the technicain who operated the rig reckoned that Bosch injectors seemed to fare less well than other injectors used in Japanese cars in terms of performance degradation. For the relatively little cost involved, suggest you get a brand new set. for some reason the Ford 19 lb injectors seem more difficult to get hold of [they show not available on Summit Racing website]. If you do go for reconditioned ones get them from someone known to be reliable like Roger.

Regards

Fred R