1985 vw quantum, bad relay or fuel pump?

No offense taken, and no IMO strong language. As I understand it, your system is simple. There is no interaction between the Jetronic and the fuel pump.    The fuel pump is solely controlled by the relay which merely senses spark, and has an initial power-on priming "pulse". Hence you fuel pump only operates when IGN is first turned on (for a few seconds) and then when spark is present - hence meeting both safety and engine requirements.    If so, the discussions with ECU interaction were irrelevant (maybe out of hand so to speak). These days ECUs control the fuel pump, and usually ignition (advance & retard). IMO these were always possible and simple to implement (except ignition for analog ECUs) and fuel pump control should always have been a part of EFI design - it simple ECU logic programming or circuitry with a single output to the fuel pump relay. But I am and was often well in advance of auto manufacturers in such matters.    [ And I compare to other systems which at the time were fully electronic - ignition and injection were totally ECU controlled, the distributor had no vacuum or speed advance mechanisms. ] Bottom line is that if that relay is reliable, then stick with it. And though easy to bypass (just a wire link), its cheap enough to carry a spare. The system I described is for the DIYers - those that want a simple and cheap system that uses common parts (an SPST or SPDT relay etc) and can be extended (eg, a manual switch to pump with the engine off). And it can be used by those with difficulties sourcing or affording the original relay. It is also easy to test. Yours isn't - you must provide ignition pulses to check the relay's operation. For DIYers, that means ensuring the vehicle is sparking, and the connection to the relay is sound. PS - I also missed your 2nd last para. Sorry - I meant no offense. You did not design your car nor the Bosch system. I did not mean that statement as a design criticism, but simply as my preferred solution. (I like readily available components and redundancy.) [ The design IMO is as stated above. Why did they NOT implement what others had, and what they now implement, and why did they change from that old implementation? It is an argument of simple logic (pun unintended) rather than technical. If the ECU provides "engine running pulses" (ignition or injectors), then why duplicate that elsewhere? It's not redundancy because if there are no ECU pulses, then the pump is not required (and for safety reasons, must be off). I'd like to know if they had technical reasons... ]

Very good overview, thanks.

As one limited in electronics, a pull and replace strategy probably should be adequate. But inability to test any one component is frustrating. But that is a much larger issue.

After my mistesting of the system, leading to blowing at least two fuel pump relays, I probably should be furious. But thanks to people like you, I have learned from the experience.

Hang in there!

I have just reread the entire thread. (With thanks to my master for that inspiration!) Your problem is simple - the relay is not getting its spark signal. That is quite clear from the early posts. The pump pumps with a normal relay (with IGN on - as it should). Good proper relays are not pumping when the engine turns. That means it is not seeing the spark signal - it merely does its initial-power on thing. What awdeclipse and then howie ll wrote were spot on, and i am not an idiot added a reason for the initial turn-on that you were hearing (since found to be a power-on timer function in the relay). I or we then got into semantics. I certainly lost track that the relay was NOT the problem. So... Does the car start with the jumper relay? (...whether a standard SPST relay else a jumper between 30 & 87 in which case the pump should be running when the IGN is on.) If yes, your relay is not seeing spark. If no, you are probably not sparking. Hence check spark with a splug HT lead connected to an external splug whose body is shorted to the engine or GND. No spark? Check with the IgCoil HT direct to the grounded spark. Yes spark? Bad dizzy cap and rotor or leads. No spark? Normally check the coil's HT lead (swap with dizzy-cap to splug lead), but since the relay isn't seeing spark, it's almost certain the IgCoil- is not being pulsed.    So then diagnose that. "How to" later if required - I suggest a new "spark" thread. If sparking and pump running, then check fuel flow, but more on that later if needed. But it seems your problem is no spark - specifically no pulses to the IgCoil.

After further review at my end, and input from others, the problem was complicated by no spark, as you wrote, and bad relays, as self-inflicted wounds (I apparently fried the two backup fuel pump relays by crossing my voltmeter's wires on the connection at the fuel pump-the connector's wires were actually crossed in the connector boot). The car now starts but stalls after 3-4 seconds.

I am not sure how to continue with this story. But I believe that I should start a new thread. I will title it "Engine starts and stalls."

Thanks for your input and patience with me!

 

I have a 1985 VW Quantum, 4 cylinder, 1.8L engine that starts and stalls within 3-4 seconds.

I can hear the fuel pump operating with the key in the on position, and then, after the engine stalls, I can hear the fuel pump still running. There is voltage on either side of the coil. The engine seems to be running pretty smoothly after starting. I tried pedal to the floor but it made no difference.

The FI system is Jetronic CIS-E. There is some background that I believe is pertinent. A couple of weeks ago, while out driving, the car was running very well when it stalled. I was able to restart it by engaging second gear, so I turned around and headed home. On the way home it stalled again and I could not start it. For a couple of days I tried checking wires, since I had earlier found several sections of wiring/connections that were bad or suspect. But as I said the car was running very well when it stalled.

Then I realized that the fuel pump was not running when I tried to start it-you can normally hear the pump priming/pressurizing with the key in the on position. I tried checking the voltage to the fuel pump rather than just inserting a new fuel pump relay. Unfortunately I misconnected the voltmeter's wires at the fuel pump connector-under the connector's boot, the wires had been crossed, so in fact I put the meter's common to the hot wire and the hot meter lead to ground. I believe that I fried two back up fuel pump relays that way. A friend confirmed that the three relays (the original and the two back ups were bad).

The friend also confirmed that the engine had no spark. Several others suggested at that point that the ignition control module was bad. They were right. My VW mechanic had some used ones for me to try. Two of them worked-the engine started, and then stalled after 3-4 seconds. I kept one of the good modules and returned the others.

The mechanic could not suggest anything else to try. But we agreed that my error with the fuel pump relays could have damaged something else, and the most likely culprit is the idle stabilization control unit. It looks like a relay,  and it is located in the relay panel. The part number, now memorized, is 811905343. It is connected to the negative side of the coil, post one, just as the ignition module is. Inside it are resistors and an IC-no mechanical coil/relay.

The mechanic said he did not know how to test it. I wrote to Telefunken asking for help testing it, but I got no answer. The only method I can think of is to switch it with a known good one in a car that runs. I am hesitant to buy a new one (cheapest -116.00) until I am sure that mine is bad. This part was also used on US spec base-model Golfs and Jettas from 1985 to 1987, but local junk yards have none of these cars anymore. Interestingly, I found the same part was used on Euro-spec Audi 80s from 1985 to 1991, and the used parts themselves are for sale on the internet through Swedish car dismantlers. I wrote to one in English but I have not heard back from them

Anyone's thoughts on this diagnosis, etc?

So it stalls with the bypass relay (standard SPST relay)? I'm just confirming since it is obvious the pump would not continue pumping after a stall if using the correct (original type) relay.

oldspark wrote: So it stalls with the bypass relay (standard SPST relay)? I'm just confirming since it is obvious the pump would not continue pumping after a stall if using the correct (original type) relay.

Good question. I am not using a "jumper" relay. I should have mentioned that the "new" relay is not exactly the same as the relay that was in place when the engine originally stalled. That one and the two back ups that I tried had the following spades: 15, 30, 87, 31 and 31b. The new one has 15, 30 31, 87 and 1 spades. The no.1 spade or rather slot in the panel is connected directly to the no 1 post on the coil and to the idle stabilization control unit, if I am reading the diagram correctly.

So when the engine stalls and the key is still in the run/start position, wouldn't the fuel pump still be "on" or presurizing, so that the operator can just turn the key to the "start" position?

Now that I think about it, the fuel pump still running after the engine stalls does not sound like a good idea. But why is it running? Could the ignition switch be fouled up, again because of the mistesting I did? I have read that the "electrical" section of the ignition switch can be shorted out through crossing wires.

There's NO electrical parts in an ignition switch. 2 switch contacts, ACC and ignition 1 and 2 and a sprung contact for the starter.

No, the pump should not run with the engine stalled with the proper relay - it is only closed when THE SPARK IS PRESENT (and during power up). Bypass the relay with a wire link.