84 VW Rabbit GTI - Hard to start when hot

Regarding my recently aquired 84 VW Rabbit GTI - manual trans - 8 valve.

I have read posts regarding topics relating to hard, hot starts but have some additional questions.

The car starts fine when it's completely cold, but takes quite a lot of cranking in order to get it to start when the engine is hot. I checked the cold start injector and found that it is working as it should on a cold start (sprays for about 8 seconds, then stops). However, the cold start injector does not operate at all on a hot start. The car does a "hot start" when I manually put 12 volts to the cold start injector for a few seconds while a helper starts the car.

The other posts suggest that the failure is in the "hot start relay". I can not find a hot start relay on the car, or referenced as a part for this car. The only thing close is the CIS/Lambda relay. Is that it?

I am about ready to add 12 volts directly to the cold start injector via a switch or, timer relay.

Any suggestions?

Thank you in advance!

Jeff

Reply to
JH
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Again a typical case of vapour lock. Fuel pressure drops off too quickly. The fuel system should hold the pressure (about 14psi) for at least

20..30min. Check for leaks and if it's a cis injection replace the o-rings of the fuel pressure regulator located in the fuel distributor.

SFC

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Reply to
SFC

Replace the fuel accumulator (near the fuel pump by the tank). The accumulator holds pressure in the system and prevents vapor lock.

Reply to
Erik Dillenkofer

TEST TEST TEST It is best to purchase some tools to monitor fuel pressure Before just throwing parts at your problem, unless price is no object. ;-)

So many items could cause your problem and it could cost you over $600 just in parts with injectors, fuel distributor, fuel pump or it's check valve or relay, fuel accumulator, plus whatever else I have forgotten about like slightly leaking fuel lines. I had to do this with a Scirocco saved from the junkyard and it needed almost everything. Started up instantly at all times though.

Reply to
One out of many Daves

I think a different control pressure regulator fixed the problem in my

84 GTI. Test pressure guage was not read>Regarding my recently aquired 84 VW Rabbit GTI - manual trans - 8 >valve.
Reply to
Jim Behning

The post alluding to vapor lock is probably correct. The CIS system is very sensitive to having sufficient residual pressure in the system when the vehicle is hot. Often the cuprit is the check valve at the fuel pump. If the smallest speck of rust gets caught in the check valve it will not close, and the fuel will return to the tank, ergo a loss of pressure. Often this can be heard, when the engine is turned off, it sounds like a series of pings coming from the area of the gas tank outet. It sometimes is immediate and other times very slow depending on the size of the speck of rust or debris. One can check this by loosening one of the bolts that seure the banjo fittings to the fuel filter --- if the check valve is faulty, there will not be a sudden release of pressure. if the check valve is ok you will get a spray of gas. One should be careful in doing this as one can get a facefull of pressurised gas if the check valve is ok. On my 81,82, and 83 rabbits there is a hot start pulse relay that is not integrated into the fuse panel --- it is in its own separate holder, usually affixed to the fuse box by tape or a tie fastener -- i have also seen them merely stuffed behind the box or dangling loose. Since i do not have a 84, i'm not sure where its located, but when functioning property, it causes fuel to be injected on an intermittant basis in very short squirts during the initial cranking. Its called a hot start pulse relay and Bentley shows its location on page 49 of section 4, above the fuse box and say it is identified by its three terminals and part no 813 906 064. Every post 1980 rabbit has the relay.

Reply to
rothring

Reply to
Jim Behning

What does this part look like?

Reply to
Dustin

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