S4 Injectors and Fuel Pump won’t engage
 

Hello all,

I have an 87 s4 that is not engaging the LH (XXV) or FP (XX) relays when turning the key to the “on” position. I removed the covers from the relays to be able to observe (they are new relays and I test each time in the horn spot before using) The EZK (XVI) relay engages. The fuel pump works when it is jumpered, I have not tried to jump the LH relay.

I have cleaned all of the grounds, but I could not get at the one on the passenger side under the MAF though.

Any advice at all on how to approach this issue would be sincerely appreciated.

TIA

They will not engage until the computers see that the engine is cranking via the crank position sensor (CPS).

Thank you.

So I went ahead and tried to start it with the EZK and the LH relays uncovered, the FP jumpered, the EZK relay energizes and the fuel pump runs but nothing happens with the LH relay.

The CPS is brand new, I used Bosch 0 261 210 002, it was cross referenced to 944-606-115-00. The CPS connector was not deteriorated in any way when I replaced it.

Telltale of CPS function is the tach needle jumps a little as you crank on the starter.

Is the CPS replacement the last thing you did to the car? If not, what did you last do to the car?

Check you have a spark when cranking, if it is good then it sounds as though your LH has gone U/S

Hi John. I don’t know how to reply to both you and Bob separately so I will just use this single post.

The CPS. The tach bounces about 100-150% stronger when I try to start itt with the new CPS installed. It bounces strong at first but then stops. Did I install the wrong CPS?

There really isn’t a good spark, there is some sort of spark but it’s not visible and not sufficient to run the engine. I think that is what I am chasing.

I get 12V to the LH relay with the key off, to all 3 of the key relays actually.

I don’t hear a clicking sound from the engine with the key on, maybe a single click or two at first but not the classic LH failure clicking.

It’s an ‘87, I’ve read about every no startt ‘87 and other 928 on Rennlist that I could find and I’ve targeted every solution that was found, including: clogged catalytic converters, relays (although I have not jumpered the LH yet), fuel injectors, CPS, coils, ignition modules, remove kickdown relay, bipass the alarm, water temp II sensor, check that the fuel line isn’t clogged, caps and rotors, changed gears to make sure it’s in Park, cleaned all of the grounds that I could reach.

I don’t know what else to do to the car. I’m wondering if my EZK is bad, because it’s relay engages but the LH and FP relays won’t.

Shark2626,
Do you have any friends? Or even acquaintances that live close enough who will plug you LH into their running car to verify the viability of your LH computer?

Monitor voltage to the relays when cranking.

Let's build a timeline on what happened and what you have done.

Was there a fail-to-start condition that caused you to replace the CPS?

What have you done to the car since it last ran correctly?

Start with "the car was running fine, then --- "

i don’t have any experience with the car running, I bought it this way as a project to build up over time. the previous owner (my neighbor) told me that it started running rich and that that got worse until it overheated so he parked it, then no start. he replaced the fuel pressure regulator and a bunch of other stuff including rebuilding LH and the MAF, but it didn’t restart and he ended up just leaving it for 2-3 years. it had spark back then but none really today, or it is so little that it’s not visible. it will fire with starter fluid but it runs unbelievably rough, rougher than imaginable, probably because of the lack of a strong spark?

i have addressed the known no start issues that I could find posted on Rennlist, but this car has a new no start issue that isn’t discussed in any of the older posts that I could find, or the solution for those cars doesn’t work on this car. basically no spark and no gas,

i think it’s electrical but I’m not experienced. the EZK relay closes but the LH and FP relays don’t. it cranks strong and pushes gas all the way through the system if the FP relay is jumped.

i pulled the LH and EZK connections and found some light corrosion which I removed and treated with deoxit. that’s the only obvious thing other than the two relays that won’t operate.

Volts with the key in the Off position, fuel pump and LH relays:

PIN:
FP 30 = 13.13
LH 30 = 13.13
FP 87 = 0
LH 87 = 0
FP 85 = -4.1
LH 85 = 2.2
FP 86 = .1
LH 86 = 13.12

The PO's rich-running is a telltale sign of LH controller failure. Walk back through the other things worked on in the fuel system and see where any mistakes may have been made.

Since it runs on starting fluid the ignition system is working. The runs-bad rough unevenly on starter fluid is typical of too much starter fluid and really rich running. If you have enough spark to run the engine, you have enough spark. If the PO had ignition wires off, trace each wire from the distro cap to the cylinders indicated on the firing order sticker. It has diagrams of the caps and the cylinders they connect to.

Without starting or even cranking the engine, install that switched jumper in the fuel pump relay socket, and verify that the fuel pressure is correct. Use a MitiVac or similar on the manifold vacuum hose to the fuel pressure regulator (rear right passenger side on US cars under the air cleaner housing) , and verify that the fuel pressure drops as expected as vacuum is increased.

Try the LH (and EZK) from your car in any other '87+ 928 to verify full functionality on a known-good engine and installation. Resist the urge to plug someone's known-good controllers into your car, so you don't damage good controllers in a potentially-dangerous car.

thanks, I will look at those issues. do you find the fuel pump relay voltages odd as compared to the lh? I really don’t know but I thought that they would be roughly the same but they are not.

the LH was rebuilt and has no time on it at all other than sitting, the maf too. the spark is so weak that it cannot be visualized, and there is no fuel reaching the cylinders (I did confirm that gas cycles back to the fuel tank by pulling the return line in the trunk). the obvious issues are that the two relays (lh and fuel pump) are not working, any suggestions about tracking down the issue?

here is what was done:

rebuilt lh and maf
new fuel pressure regulator (porsche)
new fuel filter and bosch fuel pump
new gas
new cps bosch
new temp 2 bosch
new ignition control modules bosch
new coils bosch
new relays
fuel injectors rebuilt
inspected and cleaned distributor caps, rotors, and coil wires
cleaned all grounds except the one under the pulley wheel passenger side of engine
pulled the kickdown relay
bypassed the alarm
unplugged the maf
dropped the catalytic convertors

sorry that it’s taken me awhile to reply. I sent the LH off to be tested, it checks out fine.

ive taken readings of the LH and EZK connectors with a multimeter but tbh I don’t know what to look for in all the numbers.

pulled a fuel injector connector with the battery disconnected, it reads about 2v. I’m affraid to start peeling back injector covers as I could do more damage than good, but they all appear as per new, not disturbed or obviously degraded.

im just not getting fuel from the injectors, or that’s what it seems to me. and the fuel pump won’t run unless it’s jumped. any ideas?

Put that relay back in.
What relay is in XXII? Car is an A/T, right?

ok, I will put it back in. I have a spare of that kickdown relay as well.

in XXII is a 53 relay, I didn’t know that it has a significance???

ETA yes, auto transmission